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diff --git a/docs/textdocs/BROWSING-Config.txt b/docs/textdocs/BROWSING-Config.txt new file mode 100644 index 00000000000..ba0f399f48d --- /dev/null +++ b/docs/textdocs/BROWSING-Config.txt @@ -0,0 +1,215 @@ +Date: July 5, 1998 +Contributor: John H Terpstra <jht@samba.org> + +Subject: Cross Subnet Browsing / Cross Workgroup Browsing +=============================================================================== + +OVERVIEW: +========= + +This document should be read in conjunction with BROWSING.txt and may +be taken as the 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 mapping. + + +DISCUSSION: +=========== + +Firstly, all MS Windows networking is based on SMB (Server Message +Block) based messaging. SMB messaging is implemented using 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. + +Normally, only unicast UDP messaging can be forwarded by routers. The +"remote announce" parameter to smb.conf helps to project browse announcements +to remote network segments via unicast UDP. Similarly, the "remote browse sync" +parameter of smb.conf implements browse list collation using unicast UDP. + +Secondly, in those networks where Samba is the only SMB server technology +wherever possible nmbd 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 "remote announce" and +the "remote browse sync" parameters to your smb.conf file. + +If only one WINS server is used then the use of the "remote announce" and the +"remote browse sync" parameters should NOT be necessary. + +Samba WINS does not support MS-WINS replication. This means that when setting up +Samba as a WINS server there must only be one nmbd 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 "remote browse sync" and "remote announce" +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). + +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. + + +A) Use of the "Remote Announce" parameter +------------------------------------------ +The "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 "remote announce" parameter is: + + remote announce = a.b.c.d [e.f.g.h] ... +_or_ + remote announce = a.b.c.d/WORKGROUP [e.f.g.h/WORKGROUP] ... + +where: + a.b.c.d: is either the LMB (Local Master Browser) IP address + e.f.g.h: 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. + + WORKGROUP: 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. + + +B) Use of the "Remote Browse Sync" parameter +-------------------------------------------- + +The "remote browse sync" parameter of smb.conf 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. + +The syntax of the "remote browse sync" parameter is: + + remote browse sync = a.b.c.d + +where: + a.b.c.d: is either the IP address of the remote LMB or else + is the network broadcast address of the remote segment. + + +C) Use of WINS +-------------- + +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. + +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). + +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 +"lmhosts" files that must reside on all clients in the absence of WINS. + +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. + +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. + +To configure Samba as a WINS server just add "wins support = yes" to the +smb.conf file [globals] section. + +To configure Samba to register with a WINS server just add +"wins server = a.b.c.d" to your smb.conf file [globals] section. + +DO NOT EVER use both "wins support = yes" together with "wins server = a.b.c.d" +particularly not using it's own IP address. + + +D) Do NOT use more than one (1) protocol on MS Windows machines +--------------------------------------------------------------- + +A very common cause of browsing problems results from installing more than +one protocol on an MS Windows machine. + +Every NetBIOS machine take 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. + +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. + +The safest rule of all to follow it this - USE ONLY ONE PROTOCOL! + + +E) Name Resolution Order +======================== + +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: + WINS: the best tool! + LMHOSTS: is static and hard to maintain. + Broadcast: uses UDP and can not resolve names across + remote segments. + +Alternative means of name resolution includes: + /etc/hosts: is static, hard to maintain, and lacks name_type info. + DNS: is a good choice but lacks essential name_type info. + +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: + + name resolve order = wins lmhosts bcast host +_or_ + name resolve order = wins lmhosts (eliminates bcast and host) + +the default is: + name resolve order = host lmhost wins bcast + +where: + "host" refers the the native methods used by the Unix system + to implement the gethostbyname() function call. This is normally + controlled by: + /etc/host.conf + /etc/nsswitch.conf + /etc/resolv.conf + +=============================================================================== |