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diff --git a/docs/docbook/projdoc/NetworkBrowsing.sgml b/docs/docbook/projdoc/NetworkBrowsing.sgml new file mode 100644 index 0000000000..c4b6a07777 --- /dev/null +++ b/docs/docbook/projdoc/NetworkBrowsing.sgml @@ -0,0 +1,1288 @@ +<chapter id="NetworkBrowsing"> +<chapterinfo> + &author.jht; + <pubdate>July 5, 1998</pubdate> + <pubdate>Updated: March 15, 2003</pubdate> +</chapterinfo> + +<title>Samba / MS Windows Network Browsing Guide</title> + +<para> +This document contains detailed informataion 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 addesses. WINS is +NOT involved in browse list handling except by way of name to address resolution. +</para> + +<note><para> +MS Windows 2000 and later can be configured to operate with NO NetBIOS +over TCP/IP. Samba-3 and later also supports this mode of operation. +When the use of NetBIOS over TCP/IP has been disabled then 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>What is Browsing?</title> + +<para> +To most people browsing means that 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 very complex interaction of different technologies. +The technologies (or methods) employed in making all of this work includes: +</para> + +<simplelist> + <member>MS Windows machines register their presence to the network</member> + <member>Machines announce themselves to other machines on the network</member> + <member>One or more machine on the network collates the local announcements</member> + <member>The client machine finds the machine that has the collated list of machines</member> + <member>The client machine is able to resolve the machine names to IP addresses</member> + <member>The client machine is able to connect to a target machine</member> +</simplelist> + +<para> +The samba application that controls/manages browse list management and name resolution is +called <filename>nmbd</filename>. The configuration parameters involved in nmbd's operation are: +</para> + +<para><programlisting> + Browsing options: + ----------------- + * os level + lm announce + lm interval + * preferred master + * local master + * domain master + browse list + enhanced browsing + + Name Resolution Method: + ----------------------- + * name resolve order + + WINS options: + ------------- + dns proxy + wins proxy + * wins server + * wins support + wins hook +</programlisting></para> + +<para> +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 not one of these parameters +is set nmbd will still do it's job. +</para> +</sect1> + +<sect1> +<title>Discussion</title> + +<para> +Firstly, all MS Windows networking is based on SMB (Server Message +Block) based messaging. SMB messaging may be implemented using NetBIOS or +without NetBIOS. Samba implements NetBIOS by encapsulating it over TCP/IP. +MS Windows products can do likewise. NetBIOS based networking uses broadcast +messaging to affect browse list management. When running NetBIOS over +TCP/IP this uses UDP based messaging. UDP messages can be broadcast or unicast. +</para> + +<para> +Normally, only unicast UDP messaging can be forwarded by routers. The +<command>remote announce</command> +parameter to smb.conf helps to project browse announcements +to remote network segments via unicast UDP. Similarly, the +<command>remote browse sync</command> parameter of <filename>smb.conf</filename> +implements browse list collation using unicast UDP. +</para> + +<para> +Secondly, in those networks where Samba is the only SMB server technology +wherever possible <filename>nmbd</filename> should be configured on one (1) machine as the WINS +server. This makes it easy to manage the browsing environment. If each network +segment is configured with it's own Samba WINS server, then the only way to +get cross segment browsing to work is by using the +<command>remote announce</command> and the <command>remote browse sync</command> +parameters to your <filename>smb.conf</filename> file. +</para> + +<para> +If only one WINS server is used for an entire multi-segment network then +the use of the <command>remote announce</command> and the +<command>remote browse sync</command> parameters should NOT be necessary. +</para> + +<para> +As of Samba 3 WINS replication is being worked on. The bulk of the code has +been committed, but it still needs maturation. +</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 +<command>remote browse sync</command> and <command>remote announce</command> +to affect 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 (ie: an 'if all else fails' 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 stabilise, particularly across network segments. +</para> + +</sect1> + +<sect1> +<title>How Browsing Functions</title> + +<para> +As stated above, MS Windows machines register their NetBIOS names +(ie: the machine name for each service type in operation) on start +up. Also, as stated above, 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 +<command>remote announce</command> parameter). +</para> + +<para> +Where a WINS server is used, the MS Windows client will use UDP +unicast 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 11-15 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 synchonisation +of browse lists across routed networks using the <command>remote +browse sync</command> parameter in the <filename>smb.conf</filename> file. +This causes Samba to contact the local master browser on a remote network and +to request browse list synchronisation. 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 <command>remote +browse sync</command> parameter provides browse list synchronisation - 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> +<title>Setting up Browsing in a WORKGROUP</title> + +<para> +To set up cross subnet browsing on a network containing machines +in up to be 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 any other +subnet. It is the presense of a domain master browser that makes +cross subnet browsing possible for a workgroup. +</para> + +<para> +In an 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 [global] section of the &smb.conf; file : +</para> + +<para> +<programlisting> + domain master = yes +</programlisting> +</para> + +<para> +The domain master browser should also preferrably be the local master +browser for its own subnet. In order to achieve this set the following +options in the [global] section of the &smb.conf; file : +</para> + +<para> +<programlisting> + domain master = yes + local master = yes + preferred master = yes + os level = 65 +</programlisting> +</para> + +<para> +The domain master browser may be the same machine as the WINS +server, if you require. +</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/2K/XP/2003 machine should be +able to do this, as will Windows 9x machines (although these +tend to get rebooted more often, so it's not such a good idea +to use these). To make a Samba server a local master browser +set the following options in the [global] section of the +&smb.conf; file : +</para> + +<para> +<programlisting> + domain master = no + local master = yes + preferred master = yes + os level = 65 +</programlisting> +</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 <command>local master</command> parameter allows Samba to act as a +local master browser. The <command>preferred master</command> causes nmbd +to force a browser election on startup and the <command>os level</command> +parameter sets Samba high enough so that 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 then you can disable Samba from +becoming a local master browser by setting the following +options in the <command>[global]</command> section of the +&smb.conf; file : +</para> + +<para> +<programlisting> + domain master = no + local master = no + preferred master = no + os level = 0 +</programlisting> +</para> + +</sect2> + +<sect2> +<title>Setting up Browsing in a DOMAIN</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 +name is also the Domain master browser for that name, and many +things will break if a Samba server registers the Domain master +browser NetBIOS name (<replaceable>DOMAIN</replaceable><1B>) +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 <command>[global]</command> section +of the &smb.conf; file : +</para> + +<para> +<programlisting> + domain master = no + local master = yes + preferred master = yes + os level = 65 +</programlisting> +</para> + +<para> +If you wish to have a Samba server fight the election with machines +on the same subnet you may set the <command>os level</command> 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 see the section <link linkend="browse-force-master"> +Forcing samba to be the master browser</link> +below. +</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 then +you can disable Samba from taking part in browser elections and +ever becoming a local master browser by setting following options +in the <command>[global]</command> section of the &smb.conf; +file : +</para> + +<para> +<programlisting> + domain master = no + local master = no + preferred master = no + os level = 0 +</programlisting> +</para> + +</sect2> + +<sect2 id="browse-force-master"> +<title>Forcing samba to be the master</title> + +<para> +Who becomes the <command>master browser</command> is determined by an election +process using broadcasts. Each election packet contains a number of parameters +which determine what precedence (bias) a host should have in the +election. By default Samba uses a very low precedence and thus loses +elections to just about anyone else. +</para> + +<para> +If you want Samba to win elections then just set the <command>os level</command> global +option in &smb.conf; to a higher number. It defaults to 0. Using 34 +would make it win all elections over every other system (except other +samba systems!) +</para> + +<para> +A <command>os level</command> of 2 would make it beat WfWg and Win95, but not MS Windows +NT/2K Server. A MS Windows NT/2K Server domain controller uses level 32. +</para> + +<para>The maximum os level is 255</para> + +<para> +If you want samba to force an election on startup, then set the +<command>preferred master</command> global option in &smb.conf; to "yes". 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 95 or NT or +samba) on the same local subnet both set with <command>preferred master</command> to +"yes", 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 <command>domain master browser</command>, then it is +recommended that you also set <command>preferred master</command> to "yes", 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 5 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 that browsing can occur between subnets. You can +make samba act as the domain master by setting <command>domain master = yes</command> +in &smb.conf;. By default it will not be a domain master. +</para> + +<para> +Note that you should NOT set Samba to be the domain master for a +workgroup that has the same name as an NT Domain. +</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 synchronise +browse lists. +</para> + +<para> +If you want samba to be the domain master then I suggest you also set +the <command>os level</command> high enough to make sure it wins elections, and set +<command>preferred master</command> to "yes", to get samba to force an election on +startup. +</para> + +<para> +Note that all your 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> + your local master browsers will be unable to find a domain master + browser, as it will only be looking 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> + your 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, your 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 0's broadcast and you will probably find +that browsing and name lookups won't work. +</para> +</sect2> + +<sect2> +<title>Multiple interfaces</title> + +<para> +Samba now supports machines with multiple network interfaces. If you +have multiple interfaces then you will need to use the <command>interfaces</command> +option in &smb.conf; to configure them. +</para> +</sect2> +<sect2> +<title>Use of the <command>Remote Announce</command> parameter</title> +<para> +The <command>remote announce</command> parameter of +<filename>smb.conf</filename> can be used to forcibly ensure +that all the NetBIOS names on a network get announced to a remote network. +The syntax of the <command>remote announce</command> parameter is: +<programlisting> + remote announce = a.b.c.d [e.f.g.h] ... +</programlisting> +_or_ +<programlisting> + remote announce = a.b.c.d/WORKGROUP [e.f.g.h/WORKGROUP] ... +</programlisting> + +where: +<variablelist> +<varlistentry><term><replaceable>a.b.c.d</replaceable> and +<replaceable>e.f.g.h</replaceable></term> +<listitem><para>is either the LMB (Local Master Browser) IP address +or the broadcst address of the remote network. +ie: 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 then 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 <command>Remote Browse Sync</command> parameter</title> + +<para> +The <command>remote browse sync</command> parameter of +<filename>smb.conf</filename> is used to announce to +another LMB that it must synchronise it's NetBIOS name list with our +Samba LMB. It works ONLY if the Samba server that has this option is +simultaneously the LMB on it's network segment. +</para> + +<para> +The syntax of the <command>remote browse sync</command> parameter is: + +<programlisting> +remote browse sync = <replaceable>a.b.c.d</replaceable> +</programlisting> + +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 - The Windows Internetworking Name Server</title> + +<para> +Use of WINS (either Samba WINS _or_ MS Windows NT Server WINS) is highly +recommended. Every NetBIOS machine registers it's name together with a +name_type value for each of of several types of service it has available. +eg: It registers it's name directly as a unique (the type 0x03) name. +It also registers it's 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. ie: 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 can not be used across network segments this type of +information can only be provided via WINS _or_ via statically configured +<filename>lmhosts</filename> files that must reside on all clients in the +absence of WINS. +</para> + +<para> +WINS also serves the purpose of forcing browse list synchronisation by all +LMB's. LMB's must synchronise their browse list with the DMB (domain master +browser) and WINS helps the LMB to identify it's 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> +Use of WINS will work correctly only if EVERY client TCP/IP protocol stack +has been configured to use the WINS server/s. Any client that has not been +configured to use the WINS server will continue to use only broadcast based +name registration so that 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 +<command>wins support = yes</command> to the <filename>smb.conf</filename> +file [globals] section. +</para> + +<para> +To configure Samba to register with a WINS server just add +"wins server = a.b.c.d" to your smb.conf file [globals] section. +</para> + +<important><para> +Never use both <command>wins support = yes</command> together +with <command>wins server = a.b.c.d</command> +particularly not using it's own IP address. +Specifying both will cause &nmbd; to refuse to start! +</para></important> + +<sect2> +<title>Setting up a WINS server</title> + +<para> +Either a Samba machine or a Windows NT Server machine may be set up +as a WINS server. To set a Samba machine to be a WINS server you must +add the following option to the &smb.conf; file on the selected machine : +in the [globals] section add the line +</para> + +<para> +<programlisting> + wins support = yes +</programlisting> +</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 'no' on all these machines. +</para> + +<para> +Machines with <command>wins support = yes</command> will keep a list of +all NetBIOS names registered with them, acting as a DNS for NetBIOS names. +</para> + +<para> +You should set up only ONE wins server. Do NOT set the +<command>wins support = yes</command> option on more than one Samba +server. +</para> + +<para> +To set up a Windows NT Server as a WINS server you need to set up +the WINS service - see your NT documentation for details. Note that +Windows NT WINS Servers can replicate to each other, allowing more +than one to be set up in a complex subnet environment. As Microsoft +refuse to document these replication protocols Samba cannot currently +participate in these replications. It is possible in the future that +a Samba->Samba WINS replication protocol may be defined, in which +case more than one Samba machine could be set up as a WINS server +but currently only one Samba server should have the +<command>wins support = yes</command> 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 "Primary WINS Server" field of +the "Control Panel->Network->Protocols->TCP->WINS Server" dialogs +in Windows 95 or Windows NT. To tell a Samba server the IP address +of the WINS server add the following line to the [global] section of +all &smb.conf; files : +</para> + +<para> +<programlisting> + wins server = <name or IP address> +</programlisting> +</para> + +<para> +where >name or IP address< is either the DNS name of the WINS server +machine or its IP address. +</para> + +<para> +Note that 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 +<command>wins support = yes</command> option and the +<command>wins server = <name></command> option then +nmbd 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 95, Samba and Windows NT 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> +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> +New to Samba-3 is a tool called <filename>winsedit</filename> that may be used to add +static WINS entries to the WINS database. This tool can be used also to modify entries +existing in the WINS database. +</para> + +<para> +The development of the winsedit tool was made necessary due to the migration +of the older style wins.dat file into a new tdb binary backend data store. +</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> + +<warning><para> +Do NOT use more than one (1) protocol on MS Windows machines +</para></warning> + +<para> +A very common cause of browsing problems results from installing more than +one protocol on an MS Windows machine. +</para> + +<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 precidence for winning this election process. A machine running Samba or +Windows NT will be biased so that the most suitable machine will predictably +win and thus retain it's role. +</para> + +<para> +The election process is "fought out" so to speak over every NetBIOS network +interface. In the case of a Windows 9x 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 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 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><emphasis> +Windows 95, 98, 98se, Me are referred to generically as Windows 9x. +The Windows NT4, 2000, XP and 2003 use common protocols. These are roughly +referred to as the WinNT family, but it should be recognised 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. +</emphasis></para> + +<para> +The safest rule of all to follow it this - 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> + +<simplelist> + <member>WINS: the best tool!</member> + <member>LMHOSTS: is static and hard to maintain.</member> + <member>Broadcast: uses UDP and can not resolve names across remote segments.</member> +</simplelist> + +<para> +Alternative means of name resolution includes:</para> +<simplelist> +<member>/etc/hosts: is static, hard to maintain, and lacks name_type info</member> +<member>DNS: is a good choice but lacks essential name_type info.</member> +</simplelist> + +<para> +Many sites want to restrict DNS lookups and want to avoid broadcast name +resolution traffic. The "name resolve order" parameter is of great help here. +The syntax of the "name resolve order" parameter is: +<programlisting> +name resolve order = wins lmhosts bcast host +</programlisting> +_or_ +<programlisting> +name resolve order = wins lmhosts (eliminates bcast and host) +</programlisting> +The default is: +<programlisting> +name resolve order = host lmhost wins bcast +</programlisting>. +where "host" refers the 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 <command>browse list</command>. 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 which 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, as with Samba 3 and later, 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 can NOT 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 +for samba 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 browse masters 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> +Note that you should 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> +Nmbd 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 2000 or 2003 can be configured as +your WINS server. In a mixed NT/2000/2003 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 your WINS server. +</para></note> + +<para> +To get browsing to work you need to run nmbd as usual, but will need +to use the <command>workgroup</command> 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 'unusual' purposes: announcements over the internet, for +example. See <command>remote announce</command> in the +&smb.conf; man page. +</para> +</sect2> + +<sect2> +<title>Problem resolution</title> + +<para> +If something doesn't work then hopefully the log.nmb file will help +you track down the problem. Try a debug level 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> +Note that if it doesn't work for you, then you should still be able to +type the server name as <filename>\\SERVER</filename> in filemanager then +hit enter and filemanager should display the list of available shares. +</para> + +<para> +Some people find browsing fails because they don't have the global +<command>guest account</command> 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><emphasis> +MS Windows 2000 and upwards (as with Samba) can be configured to disallow +anonymous (ie: 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 clients are not able to do this and thus will NOT be able to browse +server resources. +</emphasis></para> + +<para> +The other big problem people have is that their broadcast address, +netmask or IP address is wrong (specified with the "interfaces" option +in &smb.conf;) +</para> +</sect2> + +<sect2> +<title>Browsing across subnets</title> +<para> +Since the release of Samba 1.9.17(alpha1) Samba has been +updated to enable it to support the replication of browse lists +across subnet boundaries. New code and options have been added to +achieve this. This section describes how to set this feature up +in different settings. +</para> + +<para> +To see browse lists that span TCP/IP subnets (ie. networks separated +by routers that don't pass broadcast traffic) you must set up at least +one WINS server. The WINS server acts as a DNS for NetBIOS names, allowing +NetBIOS name to IP address translation to be done by doing a direct +query of the WINS server. This is done via a directed UDP packet on +port 137 to the WINS server machine. The reason for a WINS server is +that by default, all NetBIOS name to IP address translation is done +by 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 Win95 and WinNT, this is in the TCP/IP Properties, under Network +settings) for Samba this is in the &smb.conf; file. +</para> + +<sect3> +<title>How does cross subnet browsing work ?</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 follows : +</para> + +<para> +<programlisting> + (DMB) + N1_A N1_B N1_C N1_D N1_E + | | | | | + ------------------------------------------------------- + | subnet 1 | + +---+ +---+ + |R1 | Router 1 Router 2 |R2 | + +---+ +---+ + | | + | subnet 2 subnet 3 | + -------------------------- ------------------------------------ + | | | | | | | | + N2_A N2_B N2_C N2_D N3_A N3_B N3_C N3_D + (WINS) +</programlisting> +</para> + +<para> +Consisting of 3 subnets (1, 2, 3) connected by two routers +(R1, R2) - these do not pass broadcasts. Subnet 1 has 5 machines +on it, subnet 2 has 4 machines, subnet 3 has 4 machines. Assume +for the moment that all these machines are configured to be in the +same workgroup (for simplicities sake). Machine N1_C on subnet 1 +is configured as Domain Master Browser (ie. 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 all 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 'authoritative' 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 'trusted' +and 'verifiable' 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 'non-authoritative'. +</para> + +<para> +At this point the browse lists look as follows (these are +the machines you would see in your network neighborhood if +you looked in it on a particular network right now). +</para> + +<para> +<programlisting> +Subnet Browse Master List +------ ------------- ---- +Subnet1 N1_C N1_A, N1_B, N1_C, N1_D, N1_E + +Subnet2 N2_B N2_A, N2_B, N2_C, N2_D + +Subnet3 N3_D N3_A, N3_B, N3_C, N3_D +</programlisting> +</para> + +<para> +Note that at this point all the subnets are separate, 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 to synchronize +its browse list with. It does this by querying the WINS server +(N2_D) for the IP address associated with the NetBIOS name +WORKGROUP>1B<. This name was registerd by the Domain master +browser (N1_C) with the WINS server as soon as it was booted. +</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 MasterAnnouncement packet as a UDP port 138 packet. +It then synchronizes with it by doing a NetServerEnum2 call. This +tells the Domain Master Browser to send it all the server +names it knows about. Once the domain master browser receives +the MasterAnnouncement packet it schedules a synchronization +request to the sender of that packet. After both synchronizations +are done the browse lists look like : +</para> + +<para> +<programlisting> +Subnet Browse Master List +------ ------------- ---- +Subnet1 N1_C N1_A, N1_B, N1_C, N1_D, N1_E, + N2_A(*), N2_B(*), N2_C(*), N2_D(*) + +Subnet2 N2_B N2_A, N2_B, N2_C, N2_D + N1_A(*), N1_B(*), N1_C(*), N1_D(*), N1_E(*) + +Subnet3 N3_D N3_A, N3_B, N3_C, N3_D + +Servers with a (*) after them are non-authoritative names. +</programlisting> +</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 occured 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 look like. +</para> + +<para> +<programlisting> +Subnet Browse Master List +------ ------------- ---- +Subnet1 N1_C 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(*) + +Subnet2 N2_B N2_A, N2_B, N2_C, N2_D + N1_A(*), N1_B(*), N1_C(*), N1_D(*), N1_E(*) + +Subnet3 N3_D 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(*) + +Servers with a (*) after them are non-authoritative names. +</programlisting> +</para> + +<para> +At this point users looking in their network neighborhood on +subnets 1 or 3 will see all the servers on all sunbets, 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 recieve the missing +server entries. Finally - and as a steady state (if no machines +are removed or shut off) the browse lists will look like : +</para> + +<para> +<programlisting> +Subnet Browse Master List +------ ------------- ---- +Subnet1 N1_C 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(*) + +Subnet2 N2_B 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(*) + +Subnet3 N3_D 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(*) + +Servers with a (*) after them are non-authoritative names. +</programlisting> +</para> + +<para> +Synchronizations between the domain master browser and local +master browsers will continue to occur, but this should be a +steady state situation. +</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 neighbourhood + lists. + </para> +</listitem> + +<listitem> + <para> + Attempts to connect to these inaccessible computers will fail, but the + names will not be removed from the network neighbourhood 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, by 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> +</chapter> |