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authorJohn Terpstra <jht@samba.org>2005-04-13 04:04:36 +0000
committerGerald W. Carter <jerry@samba.org>2008-04-23 08:46:26 -0500
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+<?xml version="1.0" encoding="iso-8859-1"?>
+<!DOCTYPE chapter PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
+<chapter id="NetworkBrowsing">
+<chapterinfo>
+ &author.jht;
+ &author.jelmer;
+ <pubdate>July 5, 1998</pubdate>
+ <pubdate>Updated: April 21, 2003</pubdate>
+</chapterinfo>
+
+<title>Network Browsing</title>
+
+<para>
+This document contains detailed information as well as a fast track guide to
+implementing browsing across subnets and/or across workgroups (or domains).
+WINS is the best tool for resolution of NetBIOS names to IP addresses. WINS is
+not involved in browse list handling except by way of name to address resolution.
+</para>
+
+<note><para>
+MS Windows 2000 and later versions can be configured to operate with no NetBIOS
+over TCP/IP. Samba-3 and later versions also support this mode of operation.
+When the use of NetBIOS over TCP/IP has been disabled, the primary
+means for resolution of MS Windows machine names is via DNS and Active Directory.
+The following information assumes that your site is running NetBIOS over TCP/IP.
+</para></note>
+
+<sect1>
+<title>Features and Benefits</title>
+
+<para>
+Someone once referred to the past in these words <quote><emphasis>It was the best of times,
+it was the worst of times.</emphasis></quote> The more we look back, the more we long for what was and
+hope it never returns.
+</para>
+
+
+<para>
+<indexterm><primary>NetBIOS</primary></indexterm>
+For many MS Windows network administrators, that statement sums up their feelings about
+NetBIOS networking precisely. For those who mastered NetBIOS networking, its fickle
+nature was just par for the course. For those who never quite managed to tame its
+lusty features, NetBIOS is like Paterson's Curse.
+</para>
+
+<para>
+For those not familiar with botanical problems in Australia, Paterson's Curse,
+<emphasis>Echium plantagineum</emphasis>, was introduced to Australia from Europe during the mid-nineteenth
+century. Since then it has spread rapidly. The high seed production, with densities of
+thousands of seeds per square meter, a seed longevity of more than seven years, and an
+ability to germinate at any time of year, given the right conditions, are some of the
+features which make it such a persistent weed.
+</para>
+
+<para>
+In this chapter we explore vital aspects of Server Message Block (SMB) networking with
+a particular focus on SMB as implemented through running NetBIOS (Network Basic
+Input/Output System) over TCP/IP. Since Samba does not implement SMB or NetBIOS over
+any other protocols, we need to know how to configure our network environment and simply
+remember to use nothing but TCP/IP on all our MS Windows network clients.
+</para>
+
+<para>
+Samba provides the ability to implement a WINS (Windows Inter-networking Name Server)
+and implements extensions to Microsoft's implementation of WINS. These extensions
+help Samba to effect stable WINS operations beyond the normal scope of MS WINS.
+</para>
+
+<para>
+WINS is exclusively a service that applies only to those systems
+that run NetBIOS over TCP/IP. MS Windows 200x/XP have the capacity to operate with
+support for NetBIOS disabled, in which case WINS is of no relevance. Samba supports this also.
+</para>
+
+<para>
+For those networks on which NetBIOS has been disabled (i.e., WINS is not required)
+the use of DNS is necessary for host name resolution.
+</para>
+
+</sect1>
+
+<sect1>
+<title>What Is Browsing?</title>
+
+<para>
+To most people browsing means they can see the MS Windows and Samba servers
+in the Network Neighborhood, and when the computer icon for a particular server is
+clicked, it opens up and shows the shares and printers available on the target server.
+</para>
+
+<para>
+What seems so simple is in fact a complex interaction of different technologies.
+The technologies (or methods) employed in making all of this work include:
+</para>
+
+<itemizedlist>
+ <listitem><para>MS Windows machines register their presence to the network.</para></listitem>
+ <listitem><para>Machines announce themselves to other machines on the network.</para></listitem>
+ <listitem><para>One or more machine on the network collates the local announcements.</para></listitem>
+ <listitem><para>The client machine finds the machine that has the collated list of machines.</para></listitem>
+ <listitem><para>The client machine is able to resolve the machine names to IP addresses.</para></listitem>
+ <listitem><para>The client machine is able to connect to a target machine.</para></listitem>
+</itemizedlist>
+
+<para>
+The Samba application that controls browse list management and name resolution is
+called <filename>nmbd</filename>. The configuration parameters involved in nmbd's operation are:
+</para>
+
+<para>Browsing options: <smbconfoption name="os level"/>(*),
+ <smbconfoption name="lm announce"/>,
+ <smbconfoption name="lm interval"/>,
+ <smbconfoption name="preferred master"/>(*),
+ <smbconfoption name="local master"/>(*),
+ <smbconfoption name="domain master"/>(*),
+ <smbconfoption name="browse list"/>,
+ <smbconfoption name="enhanced browsing"/>.
+</para>
+
+<para>Name Resolution Method:
+ <smbconfoption name="name resolve order"/>(*).
+</para>
+
+<para>WINS options:
+ <smbconfoption name="dns proxy"/>,
+ <smbconfoption name="wins proxy"/>,
+ <smbconfoption name="wins server"/>(*),
+ <smbconfoption name="wins support"/>(*),
+ <smbconfoption name="wins hook"/>.
+</para>
+
+<para>
+<indexterm><primary>WINS</primary></indexterm>
+For Samba, the WINS Server and WINS Support are mutually exclusive options. Those marked with
+an (*) are the only options that commonly may need to be modified. Even if none of these
+parameters is set, <filename>nmbd</filename> will still do its job.
+</para>
+
+</sect1>
+
+<sect1 id="netdiscuss">
+<title>Discussion</title>
+
+<para>
+<indexterm><primary>SMB-based messaging</primary></indexterm>
+<indexterm><primary>NetBIOS</primary></indexterm>
+All MS Windows networking uses SMB-based messaging. SMB messaging may be implemented with or without NetBIOS.
+MS Windows 200x supports NetBIOS over TCP/IP for backwards compatibility. Microsoft appears intent on phasing
+out NetBIOS support.
+</para>
+
+<sect2>
+<title>NetBIOS over TCP/IP</title>
+
+<para>
+<indexterm><primary>encapsulating</primary></indexterm>
+<indexterm><primary>broadcast</primary></indexterm>
+<indexterm><primary>unicast</primary></indexterm>
+<indexterm><primary>UDP</primary></indexterm>
+Samba implements NetBIOS, as does MS Windows NT/200x/XP, by encapsulating it over TCP/IP.
+MS Windows products can do likewise. NetBIOS-based networking uses broadcast messaging to
+effect browse list management. When running NetBIOS over TCP/IP, this uses UDP-based messaging.
+UDP messages can be broadcast or unicast.
+</para>
+
+<para>
+<indexterm><primary>UDP</primary></indexterm>
+Normally, only uni-cast UDP messaging can be forwarded by routers. The
+<smbconfoption name="remote announce"/> parameter to smb.conf helps to project browse announcements
+to remote network segments via uni-cast UDP. Similarly, the
+<smbconfoption name="remote browse sync"/> parameter of &smb.conf;
+implements browse list collation using uni-cast UDP.
+</para>
+
+<para>
+The methods used by MS Windows to perform name lookup requests (name resolution) is determined by a
+configuration parameter called the netbios node-type. There are four (4) basic NetBIOS node types:
+</para>
+
+<indexterm><primary>b-node</primary></indexterm>
+<indexterm><primary>p-node</primary></indexterm>
+<indexterm><primary>m-node</primary></indexterm>
+<indexterm><primary>h-node</primary></indexterm>
+<indexterm><primary>node-type</primary></indexterm>
+<indexterm><primary>WINS</primary></indexterm>
+<indexterm><primary>broadcast</primary></indexterm>
+<indexterm><primary>unicast</primary></indexterm>
+<itemizedlist>
+ <listitem><para><emphasis>b-node (type 0x01):</emphasis> The Windows client will use only
+ NetBIOS broadcast requests using UDP broadcast.</para></listitem>
+ <listitem><para><emphasis>p-node (type 0x02):</emphasis> The Windows client will use point-to-point
+ (NetBIOS unicast) requests using UDP unicast directed to a WINS server.</para></listitem>
+ <listitem><para><emphasis>m-node (type 0x04):</emphasis> The Windows client will first use
+ NetBIOS broadcast requests using UDP broadcast, then it will use (NetBIOS unicast)
+ requests using UDP unicast directed to a WINS server.</para></listitem>
+ <listitem><para><emphasis>h-node (type 0x08):</emphasis> The Windows client will use
+ (NetBIOS unicast) requests using UDP unicast directed to a WINS server, then it will use
+ NetBIOS broadcast requests using UDP broadcast.</para></listitem>
+</itemizedlist>
+
+<para>
+<indexterm><primary>Hybrid</primary></indexterm>
+The default Windows network client (or server) network configuration enables NetBIOS over TCP/IP
+and b-node configuration. The use of WINS makes most sense with h-node (Hybid mode) operation so that
+in the event of a WINS breakdown or non-availability the client can use broadcast based name resolution.
+</para>
+
+<para>
+<indexterm><primary>LMB</primary><see>Local Master Browser</see></indexterm>
+<indexterm><primary>Local Master Browser</primary></indexterm>
+In those networks where Samba is the only SMB server technology, wherever possible
+<filename>nmbd</filename> should be configured on one machine as the WINS
+server. This makes it easy to manage the browsing environment. If each network
+segment is configured with its own Samba WINS server, then the only way to
+get cross-segment browsing to work is by using the
+<smbconfoption name="remote announce"/> and the
+<smbconfoption name="remote browse sync"/>
+parameters to your &smb.conf; file.
+</para>
+
+<para>
+<indexterm><primary>WINS</primary></indexterm>
+If only one WINS server is used for an entire multi-segment network, then
+the use of the <smbconfoption name="remote announce"/> and the
+<smbconfoption name="remote browse sync"/> parameters should not be necessary.
+</para>
+
+<para>
+<indexterm><primary>replication</primary><secondary>WINS</secondary></indexterm>
+As of Samba-3 WINS replication is being worked on. The bulk of the code has
+been committed, but it still needs maturation. This is not a supported feature
+of the Samba-3.0.0 release. Hopefully, this will become a supported feature
+of one of the Samba-3 release series.
+</para>
+
+<para>
+Right now Samba WINS does not support MS-WINS replication. This means that
+when setting up Samba as a WINS server, there must only be one <filename>nmbd</filename>
+configured as a WINS server on the network. Some sites have used multiple Samba WINS
+servers for redundancy (one server per subnet) and then used
+<smbconfoption name="remote browse sync"/> and <smbconfoption name="remote announce"/>
+to effect browse list collation across all segments. Note that this means clients
+will only resolve local names, and must be configured to use DNS to resolve names
+on other subnets in order to resolve the IP addresses of the servers they can see
+on other subnets. This setup is not recommended, but is mentioned as a practical
+consideration (i.e., an <quote>if all else fails</quote> scenario).
+</para>
+
+<para>
+Lastly, take note that browse lists are a collection of unreliable broadcast
+messages that are repeated at intervals of not more than 15 minutes. This means
+that it will take time to establish a browse list and it can take up to 45
+minutes to stabilize, particularly across network segments.
+</para>
+
+<para>
+When an MS Windows 200x/XP system attempts to resolve a host name to an IP address
+it follows a defined path:
+</para>
+
+<orderedlist>
+ <listitem><para>
+ Checks the <filename>hosts</filename> file. It is located in
+ <filename>%SystemRoot%\System32\Drivers\etc</filename>.
+ </para></listitem>
+
+ <listitem><para>
+ Does a DNS lookup.
+ </para></listitem>
+
+ <listitem><para>
+ Checks the NetBIOS name cache.
+ </para></listitem>
+
+ <listitem><para>
+ Queries the WINS server.
+ </para></listitem>
+
+ <listitem><para>
+ Does a broadcast name lookup over UDP.
+ </para></listitem>
+
+ <listitem><para>
+ Looks up entries in LMHOSTS, located in
+ <filename>%SystemRoot%\System32\Drivers\etc</filename>.
+ </para></listitem>
+</orderedlist>
+
+</sect2>
+
+<sect2>
+<title>TCP/IP without NetBIOS</title>
+
+<para>
+<indexterm><primary>NetBIOS</primary></indexterm>
+<indexterm><primary>NetBIOS-less</primary></indexterm>
+<indexterm><primary>DNS</primary></indexterm>
+All TCP/IP-enabled systems use various forms of host name resolution. The primary
+methods for TCP/IP hostname resolution involve either a static file (<filename>/etc/hosts</filename>)
+or the Domain Name System (DNS). DNS is the technology that makes
+the Internet usable. DNS-based host name resolution is supported by nearly all
+TCP/IP-enabled systems. Only a few embedded TCP/IP systems do not support DNS.
+</para>
+
+<para>
+<indexterm><primary>DNS</primary></indexterm>
+Windows 200x/XP can register its host name with a Dynamic DNS server. You can
+force register with a Dynamic DNS server in Windows 200x/XP using:
+<command>ipconfig /registerdns</command>.
+</para>
+
+<para>
+With Active Directory (ADS), a correctly functioning DNS server is absolutely
+essential. In the absence of a working DNS server that has been correctly configured,
+MS Windows clients and servers will be unable to locate each other, so
+consequently network services will be severely impaired.
+</para>
+
+<para>
+The use of Dynamic DNS is highly recommended with Active Directory, in which case
+the use of BIND9 is preferred for its ability to adequately support the SRV (service)
+records that are needed for Active Directory.
+</para>
+
+<para>
+Use of raw SMB over TCP/IP (No NetBIOS layer) can be done only with Active
+Directory domains. Samba is not an Active Directory Domain Controller: ergo,
+it is not possible run Samba as a domain controller and at the same time NOT use
+NetBIOS. Where Samba is used as an Active Directory Domain Member Server (DMS)
+it is possible to configure Samba to not use NetBIOS over TCP/IP. A Samba DMS
+can integrate fully into an Active Directory domain.
+</para>
+
+</sect2>
+
+<sect2 id="adsdnstech">
+<title>DNS and Active Directory</title>
+
+
+<para>
+<indexterm><primary>DNS</primary><secondary>Active Directory</secondary></indexterm>
+Occasionally we hear from UNIX network administrators who want to use a UNIX-based Dynamic
+DNS server in place of the Microsoft DNS server. While this might be desirable to some, the
+MS Windows 200x DNS server is auto-configured to work with Active Directory. It is possible
+to use BIND version 8 or 9, but it will almost certainly be necessary to create service records
+(SRV records) so MS Active Directory clients can resolve host names to locate essential network services.
+The following are some of the default service records that Active Directory requires:
+</para>
+
+<variablelist>
+<varlistentry>
+ <term>_ldap._tcp.pdc._msdcs.<emphasis>Domain</emphasis></term>
+ <listitem>
+ <para>
+ This provides the address of the Windows NT PDC for the Domain.
+ </para>
+ </listitem>
+</varlistentry>
+<varlistentry>
+ <term>_ldap._tcp.pdc._msdcs.<emphasis>DomainTree</emphasis></term>
+ <listitem>
+ <para>
+ Resolves the addresses of Global Catalog servers in the domain.
+ </para>
+ </listitem>
+</varlistentry>
+<varlistentry>
+ <term>_ldap._tcp.<emphasis>site</emphasis>.sites.writable._msdcs.<emphasis>Domain</emphasis></term>
+ <listitem>
+ <para>
+ Provides list of Domain Controllers based on sites.
+ </para>
+ </listitem>
+</varlistentry>
+<varlistentry>
+ <term>_ldap._tcp.writable._msdcs.<emphasis>Domain</emphasis></term>
+ <listitem>
+ <para>
+ Enumerates list of Domain Controllers that have the writable copies of the Active Directory data-store.
+ </para>
+ </listitem>
+</varlistentry>
+<varlistentry>
+ <term>_ldap._tcp.<emphasis>GUID</emphasis>.domains._msdcs.<emphasis>DomainTree</emphasis></term>
+ <listitem>
+ <para>
+ Entry used by MS Windows clients to locate machines using the Global Unique Identifier.
+ </para>
+ </listitem>
+</varlistentry>
+<varlistentry>
+ <term>_ldap._tcp.<emphasis>Site</emphasis>.gc._msdcs.<emphasis>DomainTree</emphasis></term>
+ <listitem>
+ <para>
+ Used by MS Windows clients to locate site configuration dependent Global Catalog server.
+ </para>
+ </listitem>
+</varlistentry>
+</variablelist>
+
+ <para>
+ Specific entries used by Microsoft clients to locate essential services for an example domain
+ called <constant>quenya.org</constant> includes:
+ </para>
+
+ <itemizedlist>
+ <listitem><para>
+ _kerberos._udp.quenya.org &smbmdash; Used to contact the KDC server via UDP.
+ This entry must list port 88 for each KDC.
+ </para></listitem>
+
+ <listitem><para>
+ _kpasswd._udp.quenya.org &smbmdash; Used to locate the <constant>kpasswd</constant> server
+ when a user password change must be processed. This record must list port 464 on the
+ master KDC.
+ </para></listitem>
+
+ <listitem><para>
+ _kerberos._tcp.quenya.org &smbmdash; Used to locate the KDC server via TCP.
+ This entry must list port 88 for each KDC.
+ </para></listitem>
+
+ <listitem><para>
+ _ldap._tcp.quenya.org &smbmdash; Used to locate the LDAP service on the PDC.
+ This record must list port 389 for the PDC.
+ </para></listitem>
+
+ <listitem><para>
+ _kpasswd._tcp.quenya.org &smbmdash; Used to locate the <constant>kpasswd</constant> server
+ to permit user password changes to be processed. This must list port 464.
+ </para></listitem>
+
+ <listitem><para>
+ _gc._tcp.quenya.org &smbmdash; Used to locate the Global Catalog server for the
+ top of the domain. This must list port 3268.
+ </para></listitem>
+ </itemizedlist>
+
+ <para>
+ The following records are also used by the Windows Domain Member client to locate vital
+ services on the Windows ADS domain controllers.
+ </para>
+
+ <itemizedlist>
+ <listitem><para>
+ _ldap._tcp.pdc._msdcs.quenya.org
+ </para></listitem>
+
+ <listitem><para>
+ _ldap.gc._msdcs.quenya.org
+ </para></listitem>
+
+ <listitem><para>
+ _ldap.default-first-site-name._sites.gc._msdcs.quenya.org
+ </para></listitem>
+
+ <listitem><para>
+ _ldap.{SecID}.domains._msdcs.quenya.org
+ </para></listitem>
+
+ <listitem><para>
+ _ldap._tcp.dc._msdcs.quenya.org
+ </para></listitem>
+
+ <listitem><para>
+ _kerberos._tcp.dc._msdcs.quenya.org
+ </para></listitem>
+
+ <listitem><para>
+ _ldap.default-first-site-name._sites.dc._msdcs.quenya.org
+ </para></listitem>
+
+ <listitem><para>
+ _kerberos.default-first-site-name._sites.dc._msdcs.queyna.org
+ </para></listitem>
+
+ <listitem><para>
+ SecID._msdcs.quenya.org
+ </para></listitem>
+ </itemizedlist>
+
+ <para>
+ Presence of the correct DNS entries can be validated by executing:
+<screen>
+&rootprompt; dig @frodo -t any _ldap._tcp.dc._msdcs.quenya.org
+
+; &lt;lt;&gt;&gt; DiG 9.2.2 &lt;lt;&gt;&gt; @frodo -t any _ldap._tcp.dc._msdcs.quenya.org
+;; global options: printcmd
+;; Got answer:
+;; -&gt;&gt;HEADER&lt;&lt;- opcode: QUERY, status: NOERROR, id: 3072
+;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 2
+
+
+;; QUESTION SECTION:
+;_ldap._tcp.dc._msdcs.quenya.org. IN ANY
+
+
+;; ANSWER SECTION:
+_ldap._tcp.dc._msdcs.quenya.org. 600 IN SRV 0 100 389 frodo.quenya.org.
+_ldap._tcp.dc._msdcs.quenya.org. 600 IN SRV 0 100 389 noldor.quenya.org.
+
+
+;; ADDITIONAL SECTION:
+frodo.quenya.org. 3600 IN A 10.1.1.16
+noldor.quenya.org. 1200 IN A 10.1.1.17
+
+
+;; Query time: 0 msec
+;; SERVER: frodo#53(10.1.1.16)
+;; WHEN: Wed Oct 7 14:39:31 2004
+;; MSG SIZE rcvd: 171
+</screen>
+ </para>
+
+</sect2>
+
+</sect1>
+
+<sect1>
+<title>How Browsing Functions</title>
+
+<para>
+MS Windows machines register their NetBIOS names
+(i.e., the machine name for each service type in operation) on start-up.
+The exact method by which this name registration
+takes place is determined by whether or not the MS Windows client/server
+has been given a WINS server address, whether or not LMHOSTS lookup
+is enabled, or if DNS for NetBIOS name resolution is enabled, etc.
+</para>
+
+<para>
+In the case where there is no WINS server, all name registrations as
+well as name lookups are done by UDP broadcast. This isolates name
+resolution to the local subnet, unless LMHOSTS is used to list all
+names and IP addresses. In such situations, Samba provides a means by
+which the Samba server name may be forcibly injected into the browse
+list of a remote MS Windows network (using the
+<smbconfoption name="remote announce"/> parameter).
+</para>
+
+<para>
+Where a WINS server is used, the MS Windows client will use UDP
+uni-cast to register with the WINS server. Such packets can be routed
+and thus WINS allows name resolution to function across routed networks.
+</para>
+
+<para>
+During the startup process an election will take place to create a
+Local Master Browser if one does not already exist. On each NetBIOS network
+one machine will be elected to function as the Domain Master Browser. This
+domain browsing has nothing to do with MS security Domain Control.
+Instead, the Domain Master Browser serves the role of contacting each local
+master browser (found by asking WINS or from LMHOSTS) and exchanging browse
+list contents. This way every master browser will eventually obtain a complete
+list of all machines that are on the network. Every 11 to 15 minutes an election
+is held to determine which machine will be the master browser. By the nature of
+the election criteria used, the machine with the highest uptime, or the
+most senior protocol version or other criteria, will win the election
+as Domain Master Browser.
+</para>
+
+<para>
+Clients wishing to browse the network make use of this list, but also depend
+on the availability of correct name resolution to the respective IP
+address/addresses.
+</para>
+
+<para>
+Any configuration that breaks name resolution and/or browsing intrinsics
+will annoy users because they will have to put up with protracted
+inability to use the network services.
+</para>
+
+<para>
+Samba supports a feature that allows forced synchronization of browse lists across
+routed networks using the <smbconfoption name="remote browse sync"/>
+parameter in the &smb.conf; file. This causes Samba to contact the local master
+browser on a remote network and to request browse list synchronization. This
+effectively bridges two networks that are separated by routers. The two remote
+networks may use either broadcast-based name resolution or WINS-based name
+resolution, but it should be noted that the
+<smbconfoption name="remote browse sync"/> parameter provides
+browse list synchronization &smbmdash; and that is distinct from name to address
+resolution. In other words, for cross-subnet browsing to function correctly it is
+essential that a name-to-address resolution mechanism be provided. This mechanism
+could be via DNS, <filename>/etc/hosts</filename>, and so on.
+</para>
+
+<sect2 id="DMB">
+<title>Configuring WORKGROUP Browsing</title>
+
+<para>
+To configure cross-subnet browsing on a network containing machines
+in a WORKGROUP, not an NT Domain, you need to set up one
+Samba server to be the Domain Master Browser (note that this is not
+the same as a Primary Domain Controller, although in an NT Domain the
+same machine plays both roles). The role of a Domain Master Browser is
+to collate the browse lists from Local Master Browsers on all the
+subnets that have a machine participating in the workgroup. Without
+one machine configured as a Domain Master Browser, each subnet would
+be an isolated workgroup unable to see any machines on another
+subnet. It is the presence of a Domain Master Browser that makes
+cross-subnet browsing possible for a workgroup.
+</para>
+
+<para>
+In a WORKGROUP environment the Domain Master Browser must be a
+Samba server, and there must only be one Domain Master Browser per
+workgroup name. To set up a Samba server as a Domain Master Browser,
+set the following option in the <smbconfsection name="[global]"/> section
+of the &smb.conf; file:
+</para>
+
+<para>
+<smbconfblock>
+<smbconfoption name="domain master">yes</smbconfoption>
+</smbconfblock>
+</para>
+
+<para>
+The Domain Master Browser should preferably be the local master
+browser for its own subnet. In order to achieve this, set the following
+options in the <smbconfsection name="[global]"/> section of the &smb.conf;
+file as shown in <link linkend="dmbexample">the following example</link>:
+</para>
+
+<para>
+<smbconfexample id="dmbexample">
+<title>Domain Master Browser smb.conf</title>
+<smbconfsection name="[global]"/>
+<smbconfoption name="domain master">yes</smbconfoption>
+<smbconfoption name="local master">yes</smbconfoption>
+<smbconfoption name="preferred master">yes</smbconfoption>
+<smbconfoption name="os level">65</smbconfoption>
+</smbconfexample>
+</para>
+
+<para>
+The Domain Master Browser may be the same machine as the WINS server, if necessary.
+</para>
+
+<para>
+Next, you should ensure that each of the subnets contains a machine that can act as
+a Local Master Browser for the workgroup. Any MS Windows NT/200x/XP machine should
+be able to do this, as will Windows 9x/Me machines (although these tend to get
+rebooted more often, so it is not such a good idea to use these). To make a Samba
+server a Local Master Browser set the following options in the
+<smbconfsection name="[global]"/> section of the &smb.conf; file as
+shown in <link linkend="lmbexample">following example</link>:
+</para>
+
+<para>
+<smbconfexample id="lmbexample">
+<title>Local master browser smb.conf</title>
+<smbconfsection name="[global]"/>
+<smbconfoption name="domain master">no</smbconfoption>
+<smbconfoption name="local master">yes</smbconfoption>
+<smbconfoption name="preferred master">yes</smbconfoption>
+<smbconfoption name="os level">65</smbconfoption>
+</smbconfexample>
+</para>
+
+<para>
+Do not do this for more than one Samba server on each subnet, or they will war with
+each other over which is to be the Local Master Browser.
+</para>
+
+<para>
+The <smbconfoption name="local master"/> parameter allows Samba to act as a
+Local Master Browser. The <smbconfoption name="preferred master"/> causes <command>nmbd</command>
+to force a browser election on startup and the <smbconfoption name="os level"/>
+parameter sets Samba high enough so it should win any browser elections.
+</para>
+
+<para>
+If you have an NT machine on the subnet that you wish to be the Local Master Browser, you can disable Samba from
+becoming a Local Master Browser by setting the following options in the <smbconfsection name="[global]"/> section of the
+&smb.conf; file as shown in <link linkend="nombexample">following example</link>:
+</para>
+
+<para>
+<smbconfexample id="nombexample">
+<title>smb.conf for not being a Master Browser</title>
+<smbconfsection name="[global]"/>
+<smbconfoption name="domain master">no</smbconfoption>
+<smbconfoption name="local master">no</smbconfoption>
+<smbconfoption name="preferred master">no</smbconfoption>
+<smbconfoption name="os level">0</smbconfoption>
+</smbconfexample>
+</para>
+
+</sect2>
+
+<sect2>
+<title>DOMAIN Browsing Configuration</title>
+
+<para>
+If you are adding Samba servers to a Windows NT Domain, then you must not set up a Samba server as a Domain Master Browser.
+By default, a Windows NT Primary Domain Controller for a domain is also the Domain Master Browser for that domain. Network
+browsing may break if a Samba server registers the domain master browser NetBIOS name (<replaceable>DOMAIN</replaceable>&lt;1B&gt;)
+with WINS instead of the PDC.
+</para>
+
+<para>
+For subnets other than the one containing the Windows NT PDC, you may set up Samba servers as Local Master Browsers as
+described. To make a Samba server a Local Master Browser, set the following options in the <smbconfsection name="[global]"/> section
+of the &smb.conf; file as shown in <link linkend="remsmb">following example</link>:
+</para>
+
+<para>
+<smbconfexample id="remsmb">
+<title>Local Master Browser smb.conf</title>
+<smbconfsection name="[global]"/>
+<smbconfoption name="domain master">no</smbconfoption>
+<smbconfoption name="local master">yes</smbconfoption>
+<smbconfoption name="preferred master">yes</smbconfoption>
+<smbconfoption name="os level">65</smbconfoption>
+</smbconfexample>
+</para>
+
+<para>
+If you wish to have a Samba server fight the election with machines on the same subnet you
+may set the <smbconfoption name="os level"/> parameter to lower levels.
+By doing this you can tune the order of machines that will become Local Master Browsers if
+they are running. For more details on this refer to <link linkend="browse-force-master">Forcing Samba to Be the Master</link> section.
+</para>
+
+<para>
+If you have Windows NT machines that are members of the domain on all subnets and you are
+sure they will always be running, you can disable Samba from taking part in browser elections
+and ever becoming a Local Master Browser by setting the following options in the
+<smbconfsection name="[global]"/> section of the &smb.conf; file as shown in <link linkend="xremmb">next example</link>:
+</para>
+
+<para>
+<smbconfexample id="xremmb">
+<title>&smb.conf; for not being a master browser</title>
+<smbconfsection name="[global]"/>
+<smbconfoption name="domain master">no</smbconfoption>
+<smbconfoption name="local master">no</smbconfoption>
+<smbconfoption name="preferred master">no</smbconfoption>
+<smbconfoption name="os level">0</smbconfoption>
+</smbconfexample>
+</para>
+
+</sect2>
+
+<sect2 id="browse-force-master">
+<title>Forcing Samba to Be the Master</title>
+
+<para>
+Who becomes the master browser is determined by an election process using broadcasts. Each election packet contains a number of parameters
+that determine what precedence (bias) a host should have in the election. By default Samba uses a low precedence and thus loses
+elections to just about every Windows network server or client.
+</para>
+
+<para>
+If you want Samba to win elections, set the <smbconfoption name="os level"/>
+global option in &smb.conf; to a higher number. It defaults to 20. Using 34 would make it win
+all elections every other system (except other samba systems).
+</para>
+
+<para>
+An <smbconfoption name="os level"/> of two would make it beat Windows for Workgroups and Windows 9x/Me, but not MS Windows
+NT/200x Server. An MS Windows NT/200x Server Domain Controller uses level 32. The maximum os level is 255.
+</para>
+
+<para>
+If you want Samba to force an election on startup, set the
+<smbconfoption name="preferred master"/> global option in &smb.conf; to <constant>yes</constant>.
+Samba will then have a slight advantage over other potential master browsers that are not Preferred Master Browsers.
+Use this parameter with care, as if you have two hosts (whether they are Windows 9x/Me or
+NT/200x/XP or Samba) on the same local subnet both set with <smbconfoption name="preferred master"/>
+to <constant>yes</constant>, then periodically and continually they will force an election in order
+to become the Local Master Browser.
+</para>
+
+<para>
+If you want Samba to be a <emphasis>Domain Master Browser</emphasis>, then it is recommended that
+you also set <smbconfoption name="preferred master"/> to <constant>yes</constant>, because
+Samba will not become a Domain Master Browser for the whole of your LAN or WAN if it is not also a
+Local Master Browser on its own broadcast isolated subnet.
+</para>
+
+<para>
+It is possible to configure two Samba servers to attempt to become the Domain Master Browser for a domain. The first server that comes
+up will be the Domain Master Browser. All other Samba servers will attempt to become the Domain Master Browser every five minutes. They
+will find that another Samba server is already the domain master browser and will fail. This provides automatic redundancy, should
+the current Domain Master Browser fail.
+</para>
+
+</sect2>
+
+<sect2>
+<title>Making Samba the Domain Master</title>
+
+<para>
+The domain master is responsible for collating the browse lists of multiple subnets so browsing can occur between subnets. You can
+make Samba act as the Domain Master by setting <smbconfoption name="domain master">yes</smbconfoption>
+in &smb.conf;. By default it will not be a Domain Master.
+</para>
+
+<para>
+Do not set Samba to be the Domain Master for a workgroup that has the same name as an NT/200x Domain.
+If Samba is configured to be the Domain Master for a workgroup that is present on the same
+network as a Windows NT/200x domain that has the same name, network browsing problems will
+certainly be experienced.
+</para>
+
+<para>
+When Samba is the Domain Master and the Master Browser, it will listen for master
+announcements (made roughly every twelve minutes) from Local Master Browsers on
+other subnets and then contact them to synchronize browse lists.
+</para>
+
+<para>
+If you want Samba to be the domain master, you should also set the
+<smbconfoption name="os level"/> high enough to make sure it wins elections, and
+set <smbconfoption name="preferred master"/> to <constant>yes</constant>, to
+get Samba to force an election on startup.
+</para>
+
+<para>
+All servers (including Samba) and clients should be using a WINS server to resolve NetBIOS names. If your
+clients are only using broadcasting to resolve NetBIOS names, then two things will occur:
+</para>
+
+<orderedlist>
+<listitem>
+ <para>
+ Local Master Browsers will be unable to find a Domain Master Browser, as they will be looking only on the local subnet.
+ </para>
+</listitem>
+
+<listitem>
+ <para>
+ If a client happens to get hold of a domain-wide browse list and a user attempts to access a
+ host in that list, it will be unable to resolve the NetBIOS name of that host.
+ </para>
+</listitem>
+</orderedlist>
+
+<para>
+If, however, both Samba and your clients are using a WINS server, then:
+</para>
+
+<orderedlist>
+<listitem>
+ <para>
+ Local master browsers will contact the WINS server and, as long as Samba has registered that it is a Domain Master Browser with the WINS
+ server, the Local Master Browser will receive Samba's IP address as its Domain Master Browser.
+ </para>
+</listitem>
+
+<listitem>
+ <para>
+ When a client receives a domain-wide browse list and a user attempts to access a host in that list, it will contact the WINS server to
+ resolve the NetBIOS name of that host. As long as that host has registered its NetBIOS name with the same WINS server, the user will
+ be able to see that host.
+ </para>
+</listitem>
+</orderedlist>
+
+</sect2>
+
+<sect2>
+<title>Note about Broadcast Addresses</title>
+
+<para>
+If your network uses a 0 based broadcast address (for example, if it ends in a 0) then you will strike problems. Windows for Workgroups
+does not seem to support a zeros broadcast and you will probably find that browsing and name lookups will not work.
+</para>
+</sect2>
+
+<sect2>
+<title>Multiple Interfaces</title>
+
+<para>
+Samba supports machines with multiple network interfaces. If you have multiple interfaces, you will
+need to use the <smbconfoption name="interfaces"/> option in &smb.conf; to configure them.
+</para>
+</sect2>
+<sect2>
+<title>Use of the Remote Announce Parameter</title>
+<para>
+The <smbconfoption name="remote announce"/> parameter of
+&smb.conf; can be used to forcibly ensure
+that all the NetBIOS names on a network get announced to a remote network.
+The syntax of the <smbconfoption name="remote announce"/> parameter is:
+<smbconfblock>
+<smbconfoption name="remote announce">a.b.c.d [e.f.g.h] ...</smbconfoption>
+</smbconfblock>
+<emphasis>or</emphasis>
+<smbconfblock>
+<smbconfoption name="remote announce">a.b.c.d/WORKGROUP [e.f.g.h/WORKGROUP] ...</smbconfoption>
+</smbconfblock>
+
+where:
+<variablelist>
+ <varlistentry><term><replaceable>a.b.c.d</replaceable> and <replaceable>e.f.g.h</replaceable></term>
+ <listitem><para>
+<indexterm><primary>LMB</primary><see>Local Master Browser</see></indexterm>
+<indexterm><primary>Local Master Browser</primary></indexterm>
+ is either the LMB (Local Master Browser) IP address or the broadcast address of the remote network.
+ i.e., the LMB is at 192.168.1.10, or the address could be given as 192.168.1.255 where the netmask
+ is assumed to be 24 bits (255.255.255.0). When the remote announcement is made to the broadcast
+ address of the remote network, every host will receive our announcements. This is noisy and therefore
+ undesirable but may be necessary if we do not know the IP address of the remote LMB.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable>WORKGROUP</replaceable></term>
+ <listitem><para>is optional and can be either our own workgroup or that of the remote network. If you use the
+ workgroup name of the remote network, our NetBIOS machine names will end up looking like
+ they belong to that workgroup. This may cause name resolution problems and should be avoided.
+ </para></listitem>
+ </varlistentry>
+</variablelist>
+</para>
+
+</sect2>
+
+<sect2>
+<title>Use of the Remote Browse Sync Parameter</title>
+
+<para>
+The <smbconfoption name="remote browse sync"/> parameter of
+&smb.conf; is used to announce to another LMB that it must synchronize its NetBIOS name list with our
+Samba LMB. This works only if the Samba server that has this option is
+simultaneously the LMB on its network segment.
+</para>
+
+<para>
+The syntax of the <smbconfoption name="remote browse sync"/> parameter is:
+
+<smbconfblock>
+<smbconfoption name="remote browse sync"><replaceable>a.b.c.d</replaceable></smbconfoption>
+</smbconfblock>
+
+where <replaceable>a.b.c.d</replaceable> is either the IP address of the
+remote LMB or else is the network broadcast address of the remote segment.
+</para>
+
+</sect2>
+
+</sect1>
+
+<sect1>
+<title>WINS &smbmdash; The Windows Inter-networking Name Server</title>
+
+<para>
+Use of WINS (either Samba WINS or MS Windows NT Server WINS) is highly
+recommended. Every NetBIOS machine registers its name together with a
+name_type value for each of several types of service it has available.
+It registers its name directly as a unique (the type 0x03) name.
+It also registers its name if it is running the LanManager compatible
+server service (used to make shares and printers available to other users)
+by registering the server (the type 0x20) name.
+</para>
+
+<para>
+All NetBIOS names are up to 15 characters in length. The name_type variable
+is added to the end of the name, thus creating a 16 character name. Any
+name that is shorter than 15 characters is padded with spaces to the 15th
+character. Thus, all NetBIOS names are 16 characters long (including the
+name_type information).
+</para>
+
+<para>
+WINS can store these 16-character names as they get registered. A client
+that wants to log onto the network can ask the WINS server for a list
+of all names that have registered the NetLogon service name_type. This saves
+broadcast traffic and greatly expedites logon processing. Since broadcast
+name resolution cannot be used across network segments this type of
+information can only be provided via WINS or via a statically configured
+<filename>lmhosts</filename> file that must reside on all clients in the
+absence of WINS.
+</para>
+
+<para>
+WINS also serves the purpose of forcing browse list synchronization by all
+LMBs. LMBs must synchronize their browse list with the DMB (Domain Master
+Browser) and WINS helps the LMB to identify its DMB. By definition this
+will work only within a single workgroup. Note that the Domain Master Browser
+has nothing to do with what is referred to as an MS Windows NT Domain. The
+later is a reference to a security environment while the DMB refers to the
+master controller for browse list information only.
+</para>
+
+<para>
+WINS will work correctly only if every client TCP/IP protocol stack
+has been configured to use the WINS servers. Any client that has not been
+configured to use the WINS server will continue to use only broadcast-based
+name registration so WINS may never get to know about it. In any case,
+machines that have not registered with a WINS server will fail name to address
+lookup attempts by other clients and will therefore cause workstation access
+errors.
+</para>
+
+<para>
+To configure Samba as a WINS server just add
+<smbconfoption name="wins support">yes</smbconfoption> to the &smb.conf;
+file [global] section.
+</para>
+
+<para>
+To configure Samba to register with a WINS server just add
+<smbconfoption name="wins server">a.b.c.d</smbconfoption>
+to your &smb.conf; file <smbconfsection name="[global]"/> section.
+</para>
+
+<important><para>
+Never use both <smbconfoption name="wins support">yes</smbconfoption> together
+with <smbconfoption name="wins server">a.b.c.d</smbconfoption>
+particularly not using its own IP address. Specifying both will cause &nmbd; to refuse to start!
+</para></important>
+
+<sect2>
+<title>WINS Server Configuration</title>
+
+<para>
+Either a Samba Server or a Windows NT Server machine may be set up
+as a WINS server. To configure a Samba Server to be a WINS server you must
+add to the &smb.conf; file on the selected Server the following line to
+the <smbconfsection name="[global]"/> section:
+</para>
+
+<para>
+<smbconfblock>
+<smbconfoption name="wins support">yes</smbconfoption>
+</smbconfblock>
+</para>
+
+<para>
+Versions of Samba prior to 1.9.17 had this parameter default to
+yes. If you have any older versions of Samba on your network it is
+strongly suggested you upgrade to a recent version, or at the very
+least set the parameter to <quote>no</quote> on all these machines.
+</para>
+
+<para>
+Machines configured with <smbconfoption name="wins support">yes</smbconfoption> will keep a list of
+all NetBIOS names registered with them, acting as a DNS for NetBIOS names.
+</para>
+
+<para>
+It is strongly recommended to set up only one WINS server. Do not set the
+<smbconfoption name="wins support">yes</smbconfoption> option on more than one Samba
+server.
+</para>
+
+<para>
+<indexterm><primary>replication</primary><secondary>WINS</secondary></indexterm>
+To configure Windows NT/200x Server as a WINS server, install and configure
+the WINS service. See the Windows NT/200x documentation for details.
+Windows NT/200x WINS servers can replicate to each other, allowing more
+than one to be set up in a complex subnet environment. As Microsoft
+refuses to document the replication protocols, Samba cannot currently
+participate in these replications. It is possible in the future that
+a Samba-to-Samba WINS replication protocol may be defined, in which
+case more than one Samba machine could be set up as a WINS server.
+Currently only one Samba server should have the
+<smbconfoption name="wins support">yes</smbconfoption> parameter set.
+</para>
+
+<para>
+After the WINS server has been configured, you must ensure that all
+machines participating on the network are configured with the address
+of this WINS server. If your WINS server is a Samba machine, fill in
+the Samba machine IP address in the <guilabel>Primary WINS Server</guilabel> field of
+the <guilabel>Control Panel->Network->Protocols->TCP->WINS Server</guilabel> dialogs
+in Windows 9x/Me or Windows NT/200x. To tell a Samba server the IP address
+of the WINS server, add the following line to the <smbconfsection name="[global]"/> section of
+all &smb.conf; files:
+</para>
+
+<para>
+<smbconfblock>
+<smbconfoption name="wins server">&lt;name or IP address&gt;</smbconfoption>
+</smbconfblock>
+</para>
+
+<para>
+where &lt;name or IP address&gt; is either the DNS name of the WINS server
+machine or its IP address.
+</para>
+
+<para>
+This line must not be set in the &smb.conf; file of the Samba
+server acting as the WINS server itself. If you set both the
+<smbconfoption name="wins support">yes</smbconfoption> option and the
+<smbconfoption name="wins server">&lt;name&gt;</smbconfoption> option then
+<command>nmbd</command> will fail to start.
+</para>
+
+<para>
+There are two possible scenarios for setting up cross-subnet browsing.
+The first details setting up cross-subnet browsing on a network containing
+Windows 9x/Me, Samba and Windows NT/200x machines that are not configured as
+part of a Windows NT Domain. The second details setting up cross-subnet
+browsing on networks that contain NT Domains.
+</para>
+
+</sect2>
+
+<sect2>
+<title>WINS Replication</title>
+
+<para>
+<indexterm><primary>replication</primary><secondary>WINS</secondary></indexterm>
+Samba-3 permits WINS replication through the use of the <filename>wrepld</filename> utility.
+This tool is not currently capable of being used as it is still in active development.
+As soon as this tool becomes moderately functional, we will prepare man pages and enhance this
+section of the documentation to provide usage and technical details.
+</para>
+
+</sect2>
+<sect2>
+<title>Static WINS Entries</title>
+
+<para>
+Adding static entries to your Samba WINS server is actually fairly easy.
+All you have to do is add a line to <filename>wins.dat</filename>, typically
+located in <filename class="directory">/usr/local/samba/var/locks</filename> or
+<filename>/var/run/samba</filename>.
+</para>
+
+<para>
+Entries in <filename>wins.dat</filename> take the form of:
+
+<programlisting>
+"NAME#TYPE" TTL ADDRESS+ FLAGS
+</programlisting>
+
+where NAME is the NetBIOS name, TYPE is the NetBIOS type, TTL is the
+time-to-live as an absolute time in seconds, ADDRESS+ is one or more
+addresses corresponding to the registration and FLAGS are the NetBIOS
+flags for the registration.
+</para>
+
+<para>
+A typical dynamic entry looks like this:
+<programlisting>
+"MADMAN#03" 1055298378 192.168.1.2 66R
+</programlisting>
+
+To make it static, all that has to be done is set the TTL to 0, like this:
+
+<programlisting>
+"MADMAN#03" 0 192.168.1.2 66R
+</programlisting>
+</para>
+
+<para>
+Though this method works with early Samba-3 versions, there is a
+possibility that it may change in future versions if WINS replication
+is added.
+</para>
+
+</sect2>
+</sect1>
+
+<sect1>
+<title>Helpful Hints</title>
+
+<para>
+The following hints should be carefully considered as they are stumbling points
+for many new network administrators.
+</para>
+
+<sect2>
+<title>Windows Networking Protocols</title>
+
+<para>
+A common cause of browsing problems results from installing more than
+one protocol on an MS Windows machine.
+</para>
+
+<warning><para>
+Do not use more than one protocol on MS Windows clients.
+</para></warning>
+
+<para>
+Every NetBIOS machine takes part in a process of electing the LMB (and DMB)
+every 15 minutes. A set of election criteria is used to determine the order
+of precedence for winning this election process. A machine running Samba or
+Windows NT will be biased so the most suitable machine will predictably
+win and thus retain its role.
+</para>
+
+<para>
+The election process is <quote>fought out</quote> so to speak over every NetBIOS network
+interface. In the case of a Windows 9x/Me machine that has both TCP/IP and IPX
+installed and has NetBIOS enabled over both protocols, the election will be
+decided over both protocols. As often happens, if the Windows 9x/Me machine is
+the only one with both protocols then the LMB may be won on the NetBIOS
+interface over the IPX protocol. Samba will then lose the LMB role as Windows
+9x/Me will insist it knows who the LMB is. Samba will then cease to function
+as an LMB and thus browse list operation on all TCP/IP-only machines will
+fail.
+</para>
+
+<para>
+Windows 95, 98, 98se, and Me are referred to generically as Windows 9x/Me.
+The Windows NT4, 200x, and XP use common protocols. These are roughly
+referred to as the Windows NT family, but it should be recognized that 2000 and
+XP/2003 introduce new protocol extensions that cause them to behave
+differently from MS Windows NT4. Generally, where a server does not support
+the newer or extended protocol, these will fall back to the NT4 protocols.
+</para>
+
+<para>
+The safest rule of all to follow is: use only one protocol!
+</para>
+
+</sect2>
+
+<sect2>
+<title>Name Resolution Order</title>
+
+<para>
+Resolution of NetBIOS names to IP addresses can take place using a number
+of methods. The only ones that can provide NetBIOS name_type information
+are:
+</para>
+
+<itemizedlist>
+ <listitem><para>WINS &smbmdash; the best tool.</para></listitem>
+ <listitem><para>LMHOSTS &smbmdash; static and hard to maintain.</para></listitem>
+ <listitem><para>Broadcast &smbmdash; uses UDP and cannot resolve names across remote segments.</para></listitem>
+</itemizedlist>
+
+<para>
+Alternative means of name resolution include:
+</para>
+<itemizedlist>
+<listitem><para>Static <filename>/etc/hosts</filename> &smbmdash; hard to maintain, and lacks name_type info.</para></listitem>
+<listitem><para>DNS &smbmdash; is a good choice but lacks essential name_type info.</para></listitem>
+</itemizedlist>
+
+<para>
+Many sites want to restrict DNS lookups and avoid broadcast name
+resolution traffic. The <parameter>name resolve order</parameter> parameter is of great help here.
+The syntax of the <parameter>name resolve order</parameter> parameter is:
+<smbconfblock>
+<smbconfoption name="name resolve order">wins lmhosts bcast host</smbconfoption>
+</smbconfblock>
+<emphasis>or</emphasis>
+<smbconfblock>
+<smbconfoption name="name resolve order">wins lmhosts (eliminates bcast and host)</smbconfoption>
+</smbconfblock>
+The default is:
+<smbconfblock>
+<smbconfoption name="name resolve order">host lmhost wins bcast</smbconfoption>
+</smbconfblock>
+where <quote>host</quote> refers to the native methods used by the UNIX system
+to implement the gethostbyname() function call. This is normally
+controlled by <filename>/etc/host.conf</filename>, <filename>/etc/nsswitch.conf</filename> and <filename>/etc/resolv.conf</filename>.
+</para>
+</sect2>
+</sect1>
+
+<sect1>
+<title>Technical Overview of Browsing</title>
+
+<para>
+SMB networking provides a mechanism by which clients can access a list
+of machines in a network, a so-called <smbconfoption name="browse list"/>. This list
+contains machines that are ready to offer file and/or print services
+to other machines within the network. Thus it does not include
+machines that aren't currently able to do server tasks. The browse
+list is heavily used by all SMB clients. Configuration of SMB
+browsing has been problematic for some Samba users, hence this
+document.
+</para>
+
+<para>
+MS Windows 2000 and later versions, as with Samba-3 and later versions, can be
+configured to not use NetBIOS over TCP/IP. When configured this way,
+it is imperative that name resolution (using DNS/LDAP/ADS) be correctly
+configured and operative. Browsing will not work if name resolution
+from SMB machine names to IP addresses does not function correctly.
+</para>
+
+<para>
+Where NetBIOS over TCP/IP is enabled, use of a WINS server is highly
+recommended to aid the resolution of NetBIOS (SMB) names to IP addresses.
+WINS allows remote segment clients to obtain NetBIOS name_type information
+that cannot be provided by any other means of name resolution.
+</para>
+
+<sect2>
+<title>Browsing Support in Samba</title>
+
+<para>
+Samba facilitates browsing. The browsing is supported by &nmbd;
+and is also controlled by options in the &smb.conf; file.
+Samba can act as a local browse master for a workgroup and the ability
+to support domain logons and scripts is now available.
+</para>
+
+<para>
+Samba can also act as a Domain Master Browser for a workgroup. This
+means that it will collate lists from Local Master Browsers into a
+wide area network server list. In order for browse clients to
+resolve the names they may find in this list, it is recommended that
+both Samba and your clients use a WINS server.
+</para>
+
+<para>
+Do not set Samba to be the Domain Master for a workgroup that has the same
+name as an NT Domain. On each wide area network, you must only ever have one
+Domain Master Browser per workgroup, regardless of whether it is NT, Samba
+or any other type of domain master that is providing this service.
+</para>
+
+<note><para>
+<command>nmbd</command> can be configured as a WINS server, but it is not
+necessary to specifically use Samba as your WINS server. MS Windows
+NT4, Server or Advanced Server 200x can be configured as
+your WINS server. In a mixed NT/200x server and Samba environment on
+a Wide Area Network, it is recommended that you use the Microsoft
+WINS server capabilities. In a Samba-only environment, it is
+recommended that you use one and only one Samba server as the WINS server.
+</para></note>
+
+<para>
+To get browsing to work you need to run nmbd as usual, but will need
+to use the <smbconfoption name="workgroup"/> option in &smb.conf;
+to control what workgroup Samba becomes a part of.
+</para>
+
+<para>
+Samba also has a useful option for a Samba server to offer itself for
+browsing on another subnet. It is recommended that this option is only
+used for <quote>unusual</quote> purposes: announcements over the Internet, for
+example. See <smbconfoption name="remote announce"/> in the
+&smb.conf; man page.
+</para>
+</sect2>
+
+<sect2>
+<title>Problem Resolution</title>
+
+<para>
+If something does not work, the <filename>log.nmbd</filename> file will help
+to track down the problem. Try a <smbconfoption name="log level"></smbconfoption> of 2 or 3 for finding
+problems. Also note that the current browse list usually gets stored
+in text form in a file called <filename>browse.dat</filename>.
+</para>
+
+<para>
+If it does not work, you should still be able to
+type the server name as <filename>\\SERVER</filename> in <command>filemanager</command>, then
+press enter and <command>filemanager</command> should display the list of available shares.
+</para>
+
+<para>
+Some people find browsing fails because they do not have the global
+<smbconfoption name="guest account"/> set to a valid account. Remember that the
+IPC$ connection that lists the shares is done as guest and, thus, you must have a valid guest account.
+</para>
+
+<para>
+MS Windows 2000 and later (as with Samba) can be configured to disallow
+anonymous (i.e., guest account) access to the IPC$ share. In that case, the
+MS Windows 2000/XP/2003 machine acting as an SMB/CIFS client will use the
+name of the currently logged-in user to query the IPC$ share. MS Windows
+9x/Me clients are not able to do this and thus will not be able to browse
+server resources.
+</para>
+
+<para>
+The other big problem people have is that their broadcast address,
+netmask or IP address is wrong (specified with the <smbconfoption name="interfaces"></smbconfoption> option
+in &smb.conf;)
+</para>
+</sect2>
+
+<sect2>
+<title>Cross-Subnet Browsing</title>
+
+<para>
+<indexterm><primary>replication</primary><secondary>browse lists</secondary></indexterm>
+Since the release of Samba 1.9.17 (alpha1), Samba has supported the
+replication of browse lists across subnet boundaries. This section
+describes how to set this feature up in different settings.
+</para>
+
+<para>
+To see browse lists that span TCP/IP subnets (i.e., networks separated
+by routers that do not pass broadcast traffic), you must set up at least
+one WINS server. The WINS server acts as a DNS for NetBIOS names. This will
+allow NetBIOS name-to-IP address translation to be completed by a direct
+query of the WINS server. This is done via a directed UDP packet on
+port 137 to the WINS server machine. The WINS server avoids the necessity
+of default NetBIOS name-to-IP address translation, which is done
+using UDP broadcasts from the querying machine. This means that machines
+on one subnet will not be able to resolve the names of machines on
+another subnet without using a WINS server.
+</para>
+
+<para>
+Remember, for browsing across subnets to work correctly, all machines,
+be they Windows 95, Windows NT or Samba servers, must have the IP address
+of a WINS server given to them by a DHCP server, or by manual configuration
+(for Windows 9x/Me and Windows NT/200x/XP, this is in the TCP/IP Properties, under Network
+settings); for Samba, this is in the &smb.conf; file.
+</para>
+
+<sect3>
+<title>Behavior of Cross-Subnet Browsing</title>
+
+<para>
+Cross-subnet Browsing is a complicated dance, containing multiple
+moving parts. It has taken Microsoft several years to get the code
+that achieves this correct, and Samba lags behind in some areas.
+Samba is capable of cross-subnet browsing when configured correctly.
+</para>
+
+<para>
+Consider a network set up as in <link linkend="browsing1">Cross-Subnet Browsing Example</link>.
+</para>
+
+<image id="browsing1">
+ <imagedescription>Cross-Subnet Browsing Example.</imagedescription>
+ <imagefile scale="40">browsing1</imagefile>
+</image>
+
+<para>
+This consists of 3 subnets (1, 2, 3) connected by two routers
+(R1, R2) which do not pass broadcasts. Subnet 1 has five machines
+on it, subnet 2 has four machines, subnet 3 has four machines. Assume
+for the moment that all machines are configured to be in the
+same workgroup (for simplicity's sake). Machine N1_C on subnet 1
+is configured as Domain Master Browser (i.e., it will collate the
+browse lists for the workgroup). Machine N2_D is configured as
+WINS server and all the other machines are configured to register
+their NetBIOS names with it.
+</para>
+
+<para>
+As these machines are booted up, elections for master browsers
+will take place on each of the three subnets. Assume that machine
+N1_C wins on subnet 1, N2_B wins on subnet 2, and N3_D wins on
+subnet 3. These machines are known as Local Master Browsers for
+their particular subnet. N1_C has an advantage in winning as the
+Local Master Browser on subnet 1 as it is set up as Domain Master
+Browser.
+</para>
+
+<para>
+On each of the three networks, machines that are configured to
+offer sharing services will broadcast that they are offering
+these services. The Local Master Browser on each subnet will
+receive these broadcasts and keep a record of the fact that
+the machine is offering a service. This list of records is
+the basis of the browse list. For this case, assume that
+all the machines are configured to offer services, so all machines
+will be on the browse list.
+</para>
+
+<para>
+For each network, the Local Master Browser on that network is
+considered <quote>authoritative</quote> for all the names it receives via
+local broadcast. This is because a machine seen by the Local Master
+Browser via a local broadcast must be on the same network as the
+Local Master Browser and thus is a <quote>trusted</quote>
+and <quote>verifiable</quote> resource. Machines on other networks that
+the Local Master Browsers learn about when collating their
+browse lists have not been directly seen. These records are
+called <quote>non-authoritative.</quote>
+</para>
+
+<para>
+At this point the browse lists appear as shown in <link linkend="browsubnet">the next example</link> (these are
+the machines you would see in your network neighborhood if you looked in it on a particular network right now).
+</para>
+
+<para>
+<table frame="all" id="browsubnet">
+ <title>Browse Subnet Example 1</title>
+ <tgroup align="left" cols="3">
+ <thead>
+ <row><entry>Subnet</entry><entry>Browse Master</entry><entry>List</entry></row>
+ </thead>
+
+ <tbody>
+ <row><entry>Subnet1</entry><entry>N1_C</entry><entry>N1_A, N1_B, N1_C, N1_D, N1_E</entry></row>
+ <row><entry>Subnet2</entry><entry>N2_B</entry><entry>N2_A, N2_B, N2_C, N2_D</entry></row>
+ <row><entry>Subnet3</entry><entry>N3_D</entry><entry>N3_A, N3_B, N3_C, N3_D</entry></row>
+ </tbody>
+ </tgroup>
+</table>
+</para>
+
+<para>
+At this point all the subnets are separate, and no machine is seen across any of the subnets.
+</para>
+
+<para>
+Now examine subnet 2. As soon as N2_B has become the Local
+Master Browser it looks for a Domain Master Browser with which to synchronize
+its browse list. It does this by querying the WINS server
+(N2_D) for the IP address associated with the NetBIOS name
+WORKGROUP&lt;1B&gt;. This name was registered by the Domain Master
+Browser (N1_C) with the WINS server as soon as it was started.
+</para>
+
+<para>
+Once N2_B knows the address of the Domain Master Browser, it
+tells it that is the Local Master Browser for subnet 2 by
+sending a <emphasis>MasterAnnouncement</emphasis> packet as a UDP port 138 packet.
+It then synchronizes with it by doing a <emphasis>NetServerEnum2</emphasis> call. This
+tells the Domain Master Browser to send it all the server
+names it knows about. Once the Domain Master Browser receives
+the <emphasis>MasterAnnouncement</emphasis> packet, it schedules a synchronization
+request to the sender of that packet. After both synchronizations
+are complete the browse lists look as shown in <link linkend="brsbex">following example</link>:
+</para>
+
+<table frame="all" id="brsbex">
+ <title>Browse Subnet Example 2</title>
+ <tgroup cols="3">
+ <colspec align="left"/>
+ <colspec align="left"/>
+ <colspec align="justify" colwidth="1*"/>
+ <thead>
+ <row><entry>Subnet</entry><entry>Browse Master</entry><entry>List</entry></row>
+ </thead>
+
+ <tbody>
+ <row><entry>Subnet1</entry><entry>N1_C</entry><entry>N1_A, N1_B, N1_C, N1_D, N1_E,
+N2_A(*), N2_B(*), N2_C(*), N2_D(*)</entry></row>
+ <row><entry>Subnet2</entry><entry>N2_B</entry><entry>N2_A, N2_B, N2_C, N2_D, N1_A(*),
+N1_B(*), N1_C(*), N1_D(*), N1_E(*)</entry></row>
+ <row><entry>Subnet3</entry><entry>N3_D</entry><entry>N3_A, N3_B, N3_C, N3_D</entry></row>
+ </tbody>
+ </tgroup>
+</table>
+
+<para>
+Servers with an (*) after them are non-authoritative names.
+</para>
+
+<para>
+At this point users looking in their network neighborhood on
+subnets 1 or 2 will see all the servers on both, users on
+subnet 3 will still only see the servers on their own subnet.
+</para>
+
+<para>
+The same sequence of events that occurred for N2_B now occurs
+for the Local Master Browser on subnet 3 (N3_D). When it
+synchronizes browse lists with the Domain Master Browser (N1_A)
+it gets both the server entries on subnet 1, and those on
+subnet 2. After N3_D has synchronized with N1_C and vica versa,
+the browse lists will appear as shown in <link linkend="brsex2">following example</link>.
+</para>
+
+<table frame="all" id="brsex2">
+ <title>Browse Subnet Example 3</title>
+ <tgroup cols="3" align="left">
+ <colspec align="left"/>
+ <colspec align="left"/>
+ <colspec align="justify" colwidth="1*"/>
+
+ <thead>
+ <row><entry>Subnet</entry><entry>Browse Master</entry><entry>List</entry></row>
+ </thead>
+
+ <tbody>
+ <row><entry>Subnet1</entry><entry>N1_C</entry><entry>N1_A, N1_B, N1_C, N1_D, N1_E,
+N2_A(*), N2_B(*), N2_C(*), N2_D(*), N3_A(*), N3_B(*), N3_C(*), N3_D(*)</entry></row>
+ <row><entry>Subnet2</entry><entry>N2_B</entry><entry>N2_A, N2_B, N2_C, N2_D, N1_A(*),
+N1_B(*), N1_C(*), N1_D(*), N1_E(*)</entry></row>
+ <row><entry>Subnet3</entry><entry>N3_D</entry><entry>N3_A, N3_B, N3_C, N3_D, N1_A(*),
+N1_B(*), N1_C(*), N1_D(*), N1_E(*), N2_A(*), N2_B(*), N2_C(*), N2_D(*)</entry></row>
+ </tbody>
+ </tgroup>
+</table>
+
+<para>
+Servers with an (*) after them are non-authoritative names.
+</para>
+
+<para>
+At this point, users looking in their network neighborhood on
+subnets 1 or 3 will see all the servers on all subnets, while users on
+subnet 2 will still only see the servers on subnets 1 and 2, but not 3.
+</para>
+
+<para>
+Finally, the Local Master Browser for subnet 2 (N2_B) will sync again
+with the Domain Master Browser (N1_C) and will receive the missing
+server entries. Finally, as when a steady state (if no machines
+are removed or shut off) has been achieved, the browse lists will appear
+as shown in <link linkend="brsex3">example below</link>.
+</para>
+
+<table frame="all" id="brsex3">
+ <title>Browse Subnet Example 4</title>
+ <tgroup cols="3" align="left">
+ <colspec align="left"/>
+ <colspec align="left"/>
+ <colspec align="justify" colwidth="1*"/>
+
+ <thead>
+ <row><entry>Subnet</entry><entry>Browse Master</entry><entry>List</entry></row>
+ </thead>
+
+ <tbody>
+ <row><entry>Subnet1</entry><entry>N1_C</entry><entry>N1_A, N1_B, N1_C, N1_D, N1_E,
+N2_A(*), N2_B(*), N2_C(*), N2_D(*), N3_A(*), N3_B(*),
+N3_C(*), N3_D(*)</entry></row>
+ <row><entry>Subnet2</entry><entry>N2_B</entry><entry>N2_A, N2_B, N2_C, N2_D, N1_A(*),
+N1_B(*), N1_C(*), N1_D(*), N1_E(*), N3_A(*), N3_B(*),
+N3_C(*), N3_D(*)</entry></row>
+ <row><entry>Subnet3</entry><entry>N3_D</entry><entry>N3_A, N3_B, N3_C, N3_D, N1_A(*),
+N1_B(*), N1_C(*), N1_D(*), N1_E(*), N2_A(*), N2_B(*),
+N2_C(*), N2_D(*)</entry></row>
+ </tbody>
+ </tgroup>
+</table>
+
+<para>
+Servers with an (*) after them are non-authoritative names.
+</para>
+
+<para>
+Synchronizations between the Domain Master Browser and Local
+Master Browsers will continue to occur, but this should remain a
+steady state operation.
+</para>
+
+<para>
+If either router R1 or R2 fails, the following will occur:
+</para>
+
+<orderedlist>
+<listitem>
+ <para>
+ Names of computers on each side of the inaccessible network fragments
+ will be maintained for as long as 36 minutes in the network neighborhood
+ lists.
+ </para>
+</listitem>
+
+<listitem>
+ <para>
+ Attempts to connect to these inaccessible computers will fail, but the
+ names will not be removed from the network neighborhood lists.
+ </para>
+</listitem>
+
+<listitem>
+ <para>
+ If one of the fragments is cut off from the WINS server, it will only
+ be able to access servers on its local subnet using subnet-isolated
+ broadcast NetBIOS name resolution. The effects are similar to that of
+ losing access to a DNS server.
+ </para>
+</listitem>
+</orderedlist>
+</sect3>
+</sect2>
+</sect1>
+
+<sect1>
+<title>Common Errors</title>
+
+<para>
+Many questions are asked on the mailing lists regarding browsing. The majority of browsing
+problems originate from incorrect configuration of NetBIOS name resolution. Some are of
+particular note.
+</para>
+
+<sect2>
+<title>How Can One Flush the Samba NetBIOS Name Cache without Restarting Samba?</title>
+
+<para>
+<indexterm><primary>flush name cache</primary></indexterm>
+Samba's <command>nmbd</command> process controls all browse list handling. Under normal circumstances it is
+safe to restart <command>nmbd</command>. This will effectively flush the Samba NetBIOS name cache and cause it
+to be rebuilt. This does not make certain that a rogue machine name will not re-appear
+in the browse list. When <command>nmbd</command> is taken out of service, another machine on the network will
+become the Browse Master. This new list may still have the rogue entry in it. If you really
+want to clear a rogue machine from the list, every machine on the network will need to be
+shut down and restarted after all machines are down. Failing a complete restart, the only
+other thing you can do is wait until the entry times out and is then flushed from the list.
+This may take a long time on some networks (perhaps months).
+</para>
+
+</sect2>
+
+<sect2>
+ <title>Server Resources Can Not Be Listed</title>
+
+<para><quote>My Client Reports <quote>This server is not configured to list shared resources</quote></quote></para>
+
+
+<para>
+Your guest account is probably invalid for some reason. Samba uses the
+guest account for browsing in <command>smbd</command>. Check that your guest account is
+valid.
+</para>
+
+<para>Also see <smbconfoption name="guest account"/> in the &smb.conf; man page.</para>
+
+</sect2>
+
+<sect2>
+ <title>I get an <errorname>`Unable to browse the network'</errorname> error</title>
+
+ <para>This error can have multiple causes:
+<indexterm><primary>browsing problems</primary></indexterm>
+ </para>
+
+ <itemizedlist>
+ <listitem><para>There is no Local Master Browser. Configure &nmbd;
+ or any other machine to serve as Local Master Browser.</para></listitem>
+ <listitem><para>You cannot log onto the machine that is the local master
+ browser. Can you logon to it as a guest user? </para></listitem>
+ <listitem><para>There is no IP connectivity to the Local Master Browser.
+ Can you reach it by broadcast?</para></listitem>
+</itemizedlist>
+</sect2>
+
+<sect2>
+<title>Browsing of Shares and Directories is Very Slow</title>
+
+<para><quote>
+<indexterm><primary>slow browsing</primary></indexterm>
+There are only two machines on a test network. One a Samba server, the other a Windows XP machine.
+Authentication and logons work perfectly, but when I try to explore shares on the Samba server, the
+Windows XP client becomes unresponsive. Sometimes it does not respond for some minutes. Eventually,
+Windows Explorer will respond and displays files and directories without problem.
+display file and directory.</quote>
+</para>
+
+<para><quote>
+But, the share is immediately available from a command shell (<command>cmd</command>, followed by
+exploration with dos command. Is this a Samba problem or is it a Windows problem? How can I solve this?
+</quote></para>
+
+<para>
+Here are a few possibilities:
+</para>
+
+<variablelist>
+ <varlistentry>
+ <term>Bad Networking Hardware</term>
+ <listitem><para>
+<indexterm><primary>bad hardware</primary></indexterm>
+<indexterm><primary>WebClient</primary></indexterm>
+ Most common defective hardware problems center around low cost or defective HUBs, routers,
+ Network Interface Controllers (NICs) and bad wiring. If one piece of hardware is defective
+ the whole network may suffer. Bad networking hardware can cause data corruption. Most bad
+ networking hardware problems are accompanied by an increase in apparent network traffic,
+ but not all.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>The Windows XP WebClient</term>
+ <listitem><para>
+ A number of sites have reported similar slow network browsing problems and found that when
+ the WebClient service is turned off, the problem disappears. This is certainly something
+ that should be explored as it is a simple solution &smbmdash; if it works.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Inconsistent WINS Configuration</term>
+ <listitem><para>
+ This type of problem is common when one client is configured to use a WINS server (that is
+ a TCP/IP configuration setting) and there is no WINS server on the network. Alternately,
+ this will happen is there is a WINS server and Samba is not configured to use it. The use of
+ WINS is highly recommended if the network is using NetBIOS over TCP/IP protocols. If use
+ of NetBIOS over TCP/IP is disabled on all clients, Samba should not be configured as a WINS
+ server neither should it be configured to use one.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Incorrect DNS Configuration</term>
+ <listitem><para>
+ If use of NetBIOS over TCP/IP is disabled, Active Directory is in use and the DNS server
+ has been incorrectly configured. Refer <link linkend="adsdnstech">DNS and Active Directory</link> for more information.
+ </para></listitem>
+ </varlistentry>
+</variablelist>
+
+</sect2>
+</sect1>
+</chapter>