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List:       linux-virtual-server
Subject:    Re: [lvs-users] LVS-NAT problems for SMTP cluster - SOLVED
From:       infernix <infernix () infernix ! net>
Date:       2008-05-04 0:26:32
Message-ID: 481D02B8.2030607 () infernix ! net
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infernix wrote:
> No, not really. Look at the twake or tcpdump logs; the realserver keeps 
> retransmitting the TCP packets but the client doesn't seem to tie them 
> to the active TCP session (regardless of what client is used, whether a 
> local address in the public range or any random public IP on the 
> internet). So it seems that something is going wrong with the TCP 
> session.

And so I had another look at the output - this time in wiresharks GUI 
mode - and noticed TCP checksum errors on all the packets sent *to* the 
client.

Had I read LVS-HOWTO.virtualised_realservers.html I would've known that 
on Xen there is an issue with tcp checksumming messing it all up. So I 
disabled rx checksums with ethtool on the ethX interfaces of the 
director and realservers, and all was well with the world again. I 
probably should've mentioned that all machines in this test scenario are 
Xen VMs :)

infernix


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