Fw: [Samba] LDAP redudancy problem

Alain.Gorlier at altissemiconductor.com Alain.Gorlier at altissemiconductor.com
Mon Apr 30 16:13:07 GMT 2007

Doing some other tests, we determinate that the problem occurs when 
Fileservers and Ldap servers are not on the same IP subnet.
When they are on different subnets, the TCP timeout is about 3 minutes. We 
could change some kernel IP settings (as syn_retries) but we do not want 
to do that....another side effects would occur....
As the samba 'ldap timeout' parameter seems to be effective for "global" 
URI (master+replica), there is no fail over before 3 minutes. 
So, we would have to setup "ldap timeout" from 15 seconds to 3 minutes to 
make it work but it's too much longer...

If we are on the same subnet, ARP timeout occurs.
As the master server is down, the corresponding arp entry on the 
fileserver expires about 30 seconds later, then the arp entry is set to 
"incomplete" and the timeout is now about 6 seconds !
So,  30 seconds after the Master ldap server is down, Samba server 
switches to Replica server after only 6s for each new client connection.

I would prefer 'samba' ldap timeout failover parameter instead of 
different network timeouts corresponding to different network 
architectures....Don't you think ?

Has anybody ever test LDAP redundancy with different IP subnets ?


Redhat 4, Samba server 3.0.22.

We are testing LDAP redudancy. We have 2 LDAP servers.

If we stop LDAP services on the first LDAP server, everything works fine : 

the samba server detects the failed ldap server and switch to the 
available LDAP server.
Clients can be authenticated, everything works fine.

But, if the first LDAP server is unavailable (does not respond to ping), 
the samba server does not swith to the second LDAP server :

[2007/04/20 09:36:46, 0] lib/smbldap.c:smbldap_search_suffix(1346)
  smbldap_search_suffix: Problem during the LDAP search:  (Time limit 
[2007/04/20 09:36:46, 2] auth/auth.c:check_ntlm_password(317)
  check_ntlm_password:  Authentication for user [adminocs] -> [adminocs] 
[2007/04/20 09:36:46, 2] smbd/server.c:exit_server(614)
  Closing connections

We have tried using smaller and greater values of ldap timeout in smb.conf 

but it does not help. ( from 5 to 600)
We have tried using smaller and greater values in the /etc/ldap.conf for 
bind_timelimit and timelimit (30 by default, from 5 to 300), but it does 
not help.

Here is our smb.conf related to ldap :

        passdb backend = ldapsam:"ldap://itdsd1l1.altissemiconductor.com 
        ldap passwd sync = Yes
        ldap admin dn = 
        ldap suffix = ou=manuf,o=altissemiconductor.com,cn=mfg
        ldap group suffix = ou=Groups
        ldap user suffix = ou=Users
        ldap machine suffix = ou=Computers
        ldap timeout = 15
        ldap ssl = start_tls

Is there a way to change the bind timeout for samba server to switch to 
the available node before the "search time limit exceeded" ?
Do I miss something ?


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