Browsing across subnets - some more problems

[John D. Blair]

Graham Leggett wrote:
Graham,

> I am still battling to get browsing across subnets to work.

It takes a while to figure it out!
 
> I just need some clarification on some issues. I understand the
> following things to be the case, please correct me if I am wrong:

Sure thing.
 
> - Machines on a subnet will periodically announce their existance by
> broadcasting to everyone their identity

Clarification: broadcasting to everyone on their network.  Machines on
broadcast isolated networks will not see the announcement.

> - Other machines will hear these broadcasts, and add the machines to
> their browse lists.

Yes.  Other machines on the same network.

> - If one of the machines is a WINS server, that machine will keep note
> of the broadcasting machine in it's WINS database, as well aqs add the
> machine to it's browse list.

Not true, though this is a very common error.  WINS is almost completely
seperate from the browsing mechanism.  WINS provides a means for mapping
NetBIOS names to IP addresses.  If a host has been configured to use a
WINS server it contacts the WINS server when it wants to register a
NetBIOS name.  Otherwise it just broadcasts a registration announcement.

The browse list is maintained on each network by a "master browser". 
The master browser is selected by election.  This machine is responsible
for listening to name registration announcements and producing a browse
list.

I said above that WINS is *almost* completely seperate from browsing b/c
WINS does get a little involved with browsing if your network stretches
across multiple broadcast isolated TCP/IP networks.  Each master browser
asks the WINS server if there is a domain master browser.  If there is,
the master browser becomes a "local master browser", responsible for
maintaining a browse list for its own network.  Periodically, each local
master browser synchronizes its browse list with the domain master
browser.  If you have several networks it may take quite some time
before your browse list in each network is completely correct.

This is all pretty well explained in BROWSING.txt.  I suggest you read
through it and work through the examples until your comfortable with how
it works.
 
> I am not getting the above, here are some questions / concerns:
> 
> - Why does nmbd appear to be running twice on some machines?

nmbd, like smbd is a "fork and exec" daemon.  When a new request comes
it, it forks.  This new image deals with the request, while the parent
process waits for new requests.

> - Why does the samba WINS server add machines to it's WINS database, but
> not add machines to its browse list?

Explained above.  WINS and the browse list are independant of each
other.
 
> - Why does another samba server not receive an updated browse list from
> the WINS server?

Again, because the WINS server doesn't have a browse list.  Yes, this
seems the *logical* thing to do, but remember, this is Microsoft!  To be
fair, the master browser mechanism was developed before TCP/IP was used
as a transport protocol for SMB.  With NetBEUI and IPX a WINS server is
not needed b/c each host can broadcast to all other hosts.  (NetBEUI is
a single network protocol-- it can't be routed, and IPX allows
broadcasting across the entire XNS/Novell internetwork).  It wasn't
until people tried to encapsulate NetBIOS in TCP/IP that broadcasting
was no longer a reliable technique for contacting all other hosts.
 
> Any ideas?

far too many :)

hope this helps...
 -john.

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John D. Blair          (sys|net)admin, the university computer center
mailto:jdblair at uab.edu                    u. of alabama at birmingham
phoneto:(205) 975-7123                        (my other car is a cdr)
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