[Fwd: Multiple Wins Servers]

Welsh, Armand armand.welsh at sscims.com
Wed Jan 3 18:46:01 GMT 2001

not completely true.  It's common practice to have two wins servers on a
network, replicating with each other, and having the clients point to both
wins servers.  This allows for either of the two wins server to crash, and
wins lookups still work.  This is simple to do on NT, and as I said, is
common practice.  What happens is that the client registers itself with the
primary, if it can't see the primary, then it registers on the secondary.
Once it's registerd on the wins server, the wins server replicate with each
other, so if a wins server crashes, the back server knows about the hosts
that were listed on the primary wins server.  The problem with this, is that
if the a wins server crashes, the hosts must be restarted, to re-register
their names on the new wins server, or wait a very, very long time.  This
re-registration is not a problem for clients, as their names don't need to
be resolvable, only the servers.

What windows clients do, is to query the primary, if the name is not found,
regardless of the reason, then the secondary is querried, if the name is
still not found, then and only then is the name lookup considered a failure.
If the primary responds with a host's ip address, then that address is used,
and the secondary wins server is never querried.  (if I understand it

the wins replication is not a problem, when the failed server comes back on
line.  I assume it's because it will to a database reconsilation, to purge
any locally listed hosts that exist in the replicated servers' lists as
local.  Or it must reset the local cache (access database actually) on
system startup.  I am not sure which condition is applied, as I haven't done
this in a while.... But it does work.

So if it works on NT, there really isn't any real reason it can't be made to
work in samba.


-> -----Original Message-----
-> From: Christopher R. Hertel [mailto:crh at nts.umn.edu]
-> Sent: Wednesday, January 03, 2001 10:29 AM
-> To: Danny Travis
-> Cc: samba-technical at us5.samba.org
-> Subject: Re: [Fwd: Multiple Wins Servers]
-> The HEAD development branch includes partial support for 
-> WINS failover.  
-> That is, you can enter a semicolon-delimited list of WINS 
-> servers.  Once 
-> this bit of code is complete, if the first WINS server goes 
-> down Samba 
-> will switch to using the second, etc.
-> The problem is that there is code in Samba that stores the 
-> WINS server
-> address and uses that to identify packets coming from WINS.  
-> This is an
-> important bit of code, and I didn't write it.  I have asked 
-> for guidance
-> from the author of that code to ensure that I don't mess things up.
-> NMBD is designed such that has a single process listening 
-> for packets, and
-> this code is responsible for assuring that the incomming packets are
-> correctly assigned to their respective awaiting 
-> transactions.  I don't
-> want to mess that up. The author of that piece has promised 
-> to help me
-> out, but has been quite busy with much more important fixes and
-> improvements. 
-> Regarding the ability to query multiple WINS servers (as 
-> opposed to simple
-> failover):  There was much debate about this when the 
-> failover code was
-> proposed (I no longer remember who first proposed it, but 
-> they provided
-> code which was quite nice).  My own further research 
-> suggests that this is
-> a *really bad idea*.  RFC1001/1002 specifically warns 
-> against allowing a
-> host to see disjoint name spaces, as this will result in 
-> name conflicts. 
-> Chris -)-----
-> -- Start of included mail From:  Danny Travis 
-> <danny_travis at email.mobil.com>
-> > X-Mozilla-Status2:  00000000
-> > Date:  Wed, 03 Jan 2001 11:02:39 -0600
-> > X-Accept-Language:  en
-> > To:  samba at lists.samba.org
-> > Subject:  Multiple Wins Servers
-> > Can Samba be configured to point to multiple wins servers? 
-> It looks like
-> > the wins server option only allows for one IP address.
-> > 
-> -- End of included mail.
-> -- 
-> Christopher R. Hertel -)-----                   University 
-> of Minnesota
-> crh at nts.umn.edu              Networking and 
-> Telecommunications Services
->     Ideals are like stars; you will not succeed in touching them
->     with your hands...you choose them as your guides, and following
->     them you will reach your destiny.  --Carl Schultz

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