[lvs-users] LVS-NAT problems for SMTP cluster

[Kees Hoekzema]

> -----Original Message-----
> I'm just typing the commands in the telnet session  to see whether if
> the real server receives them at all. Doesn't seem to be the case, yet
> there is tcp traffic going al the way. And no, there's no banner, nor
> do I see the data in the tshark log (the TCP Retransmits).

What happens if you test it, without testing the SMTP server?
If you shut down the SMTP server and run 'nc -p 25 -l' (netcat)

That way you do not test if the SMTP server is actually accepting
connections, but you test if the data comes through. You should see whatever
you type in telnet getting echo'ed on the realserver and whatever you type
in the netcat, you should see in the telnet client. If that works, it seems
like a problem with the mailserver rather than the loadbalancer.

Anyway, I had a similar problem with the IP's from the mailservers not
matching the address they had. mail.domain.net resolved to x.x.x.11, while
mail from the mailserver behind the NAT came from x.x.x.3. I fixed that by
adding:
iptables  --table nat --append POSTROUTING --source $mailserverRIP --jump
SNAT --to-source x.x.x.11

While I also had:
iptables  --table nat --append POSTROUTING --source $internalNetwork --jump
MASQUERADE

(make sure the DNAT rule is before the MASQ rule)
That solved the problem of mails send from the realservers not having the
same IP.

I hope that was useful, good luck testing!

-kees
> 
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