[Samba] Domain logins across subnets

[John Paul]

Greetings,

My environment is Samba 3.0.23d as a PDC, password backend is OpenLDAP 2.3.27, 
running on SuSE 10.1; workstations are Windows XP SP2, all recent patches 
applied. All machines are on the same Class B private IP network. Domain 
logons function perfectly, performance is very nice. For security and performance 
reasons we are looking at dividing the network into many VLANS, each with 
its own IP subnet. 

On the testing network, a very strange thing is happening. When the workstation 
is on the Class B subnet, all functions work perfectly - Adding machine to 
domain, logging in, mapping drive to samba server, etc. However, when placed 
on the test VLAN (a class C private IP subnet) some of this functionality 
goes away. I can ping the DC (meaning the packets are correctly routed). 
I can resolve the DC name to its IP (meaning name resolution across the subnet 
is working), I can resolve my own workstation name to the correct IP. However, 
when I try to add this machine to the domain, I get the following error:

The following error occurred attempting to join the domain "DOMAIN"

Logon Failure: unknown user name or bad password.

Of course I'm using the same user name and password (root) as I use
when on the Class B subnet. When I attempt to map a drive, I get "System
error 1326 has occurred - Logon failure: unknown user name or bad
password." Stranger yet is that every 5 or so times, this all works
perfectly.

I've considered problems with the switching hardware, however, I set the 
workstation to ping the DC constantly for like 4 hours and not a single packet 
was dropped. There is nothing strange about the setup, it's really very simple. 
All other services function perfectly between the VLANS. I also tried adding 
a VLAN on our production network using the production DC with the exact same 
results.

I should add that on the testing network, although the logical layout
is similar, we do not have a DHCP server so all address assignments are
done by hand. However, when we move the workstation from one subnet to
another, we are careful to put the workstation in the correct subnet and
make sure that the WINS server is set correctly.

I've attached my smb.conf. If any party is interested in further diagnosing 
the problem I'll be happy spend as much time as necessary to provide the 
information you might need.

Here's my smb.conf (names have been changed to protect the guilty)

[global]
interfaces = eth0 lo
bind interfaces only = yes
workgroup = DOMAIN
server string = "Domain Controller"
passdb backend = ldapsam:ldap://127.0.0.1
log level = 1
syslog = 0
log file = /usr/local/samba/var/log.%m
max log size = 2500
name resolve order = wins hosts bcast
time server = Yes
show add printer wizard = No
add user script = /var/lib/samba/sbin/smbldap-useradd.pl -a -m
'%u'
delete user script = /var/lib/samba/sbin/smbldap-userdel.pl
'%u'
add group script = /var/lib/samba/sbin/smbldap-groupadd.pl -p
'%g'
delete group script = /var/lib/samba/sbin/smbldap-groupdel.pl
'%g'
add user to group script =
/var/lib/samba/sbin/smbldap-groupmod.pl -m '%u' '%g'
delete user from group script =
/var/lib/samba/sbin/smbldap-groupmod.pl -x '%u' '%g'
set primary group script =
/var/lib/samba/sbin/smbldap-usermod.pl -g '%g' '%u'
add machine script = /var/lib/samba/sbin/smbldap-useradd.pl -w
'%u'
logon script = netlogon.cmd
logon path = \\dc\profiles\%U ( file://\dcU )
logon home = \\dc\profiles\%U ( file://\dcU )
domain logons = Yes
os level = 75
preferred master = Yes
domain master = Yes
wins support = Yes
ldap admin dn = cn=Manager,dc=example,dc=org
ldap group suffix = ou=group
ldap idmap suffix = ou=Idmap
ldap machine suffix = ou=people
ldap suffix = dc=example,dc=org
ldap user suffix = ou=people
idmap backend = ldap://127.0.0.1
idmap uid = 10000-20000
idmap gid = 10000-20000
profile acls = Yes
map acl inherit = Yes

[netlogon]
comment = "Net logon share"
path = /netlogon
write list = root

[profiles]
comment = "Roaming profile share"
path = /profiles
read only = No
hide files = /desktop.ini/Desktop.ini/DESKTOP.INI/
csc policy = disable
create mask = 0700
force create mode = 0700
directory mask = 0700
force directory mode = 0700