Multiple subnets and browsemaster wars.

Christopher R. Hertel crh at
Wed Mar 29 16:35:07 GMT 2000

> > >  Im having a browsing problem with a subnetted network.
> > >  At the centre is samba 2.0.6 on a DU box. Works well.
> > 
> > A quick check... make sure that those evil PCs don't have NetBIOS bound to
> > more than one protocol.  If NetBIOS is bound to NetBEUI or NWLink then
>  We are doing that. Unfortunatly we don't know where all the PCs are
> (some are laptops) and some people don't belive us about only having
> TCP/IP installed and reinstall netbeui or IPX
> after we leave :-(.

There's another thread on this list that has some very good information
about just what goes wrong when NetBIOS is bound to multiple protocol
stacks.  Look for '"unbecome lmb" oddity'.  Herb summed it up well.

> At any rate if they have the WINS stuff correct,
> even though I get a browse master war happening, they at least sync the
> browse list with the master server and all works from the client point
> of view. Its when some PC that IS NOT configured with our WINS server
> address wins that things break, and I can't see a way to detect that
> easly - as the offending local browsemaster doesnt register with our
> WINS server. 

Hmmm... If the WINS server isn't set correctly you are likely to get
mangled name space.  The next question is whether the PCs are all set up
as H nodes or not.  I think H is the default for Windows these days.


> Note some of the 'rouge' broken PC's have the wrong netmask
> set. An historical accident. (The LAN here was once one large class 'B'
> range. It was then subnetted, but for years no one bothered to configure
> client machines properly. Proxy arp fixed the inconsistancies so no one
> cared.)

Yes, this will further mess up the name space because the PCs with broken
netmasks may not pick up the broadcast announements.  This will also
mangle browse list management.

>  The main issue - since I have broadcast forwarding, I dont REALY need a
> browse master in each subnet do I?. 

Um...  You need a browse master in in broadcast domain.  The broadcast
domain is the set of machines that can hear broadcasts from each other. 
As you've already stated, the netmasks and broadcast addresses are not set
correctly.  A message sent to will get through, I believe,
but if you've got a /24 network and send a broadcast to a /16 subnet mask
that likely won't work.

> The workstation broadcast for name
> resoultion or browse lists will get forwarded to the samba server.

Yes, but Samba's NBNS server (WINS) won't pick up broadcasts so the name 
won't be entered into the WINS database (if that's on Samba).  Actually, 
I don't believe that Microsoft's WINS will pick up broadcasts either.

Samba and Windows will both send out a broadcast request (in addition to a
WINS query) if they want to resolve a name, but that is *separate* from 
the WINS mechanism.

> I assume it can answer back to the remote subnet. What I appear to need is
> some what to have the central samba server's 'im the browse master' sent
> back to the subnets so some win9x client doesnt think It has to be a
> master, and initiates an election which the main samba server see's.

Normally, an H node will to a WINS lookup first and, if that fails, follow
it up with a broadcast.

The LMB lookup may be a special case, however, since there should be a
single LMB per broadcast space.  I don't yet know how Windows goes about
finding local master and local backup browsers.  I need to study that. 
However, listing _MSBROWSE_ in the WINS database would only work if it
were listed as a group name.  In the case of a group name, Microsoft's
WINS (incorrectly) stores only the address.  Samba follows
suit, though we are considering fixing this to be closer to the RFCs (thus
providing better support for OS/2 systems). 

In any case, the end result is that the Windows clients will wind up doing
a broadcast name lookup in order to find the local master browser and any
backup browsers. 

In theory, this means that the one-lmb-per-broadcast-range should work.  
The problem, then, comes back to the non-orthogonal broadcast domain you 
seem to have.

Having NetBIOS bound to multiple protocols on some stations, and having
incorrect subnet masks & broadcast addresses, will mess up your broadcast
domain, which is at the heart of the problem.


Hope that helped!

Chris -)-----

Christopher R. Hertel -)-----                   University of Minnesota
crh at              Networking and Telecommunications Services

    Ideals are like stars; you will not succeed in touching them
    with your choose them as your guides, and following
    them you will reach your destiny.  --Carl Schultz

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