[lvs-users] Session "persistence" issues

Elliott Barrere elliott at barrere.us
Mon Sep 22 21:04:40 BST 2014

Hi guys -

I'm having an issue with a 2-node setup (similar setup to what's described here) where established sessions to a particular real server don't fail over when that real server fails.  That is, if a connection exists in the LVS connection state table and that real server goes down, the connections to that real server persist, rather than being cleared from the table as I would expect.

My test in a little more detail:

1) Start my service on realserver1 ONLY and open a connection (thus forcing a connection to realserver1)
2) Stop the service on realserver1 and start it on realserver2, verifying "ipvsadm -Ln" shows realserver1 down and realserver2 up
3) Establish a "new" connection to the VIP, forcing the same source port & IP with nc
4) The connection fails, trying to connect to realserver1 (verified by tcpdump)

It appears that this is because the state table still contains an entry for "SRCIP:SRCPORT VIP:DSTPORT realserver1:DSTPORT".  I am new to LVS, but I assume this is not the expected behavior, because it seems it would be a fairly typical scenario if both load balancers were, for example, behind a PAT firewall.

Can anyone shed some light on this, and how I might possibly fix it?  I am new to LVS so any help is appreciated!

Cheers -

elliott barrere | 206.351.3520

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