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[lvs-users] Routing issue (regarding load balancing and expires time)

To: British Ubuntu Talk <ubuntu-uk@xxxxxxxxxxxxxxxx>, Birmingham Linux User Group <sb@xxxxxxxxxxxxxxxxxx>, lvs-users@xxxxxxxxxxxxxxxxxxxxxx
Subject: [lvs-users] Routing issue (regarding load balancing and expires time)
From: Andrew Loughran <andy@xxxxxxxx>
Date: Tue, 24 Feb 2009 09:32:22 +0000
Hi,

This is my first post so please feel free to point out any slips in
netiquette...

I'm using ip route to create a load-balanced use of 2 internet connections,
in most respects it works correctly - i.e. traffic gets routed over both
connections. However, one 'feature' of the load balancing is that routes get
cached and don't change if they're in more or less continuous use - this is
exactly the behaviour I need. Unfortunately some routes don't seem to behave
like this and it seems to be the ones with an 'expires' time. For example I
have:

atom3:~# ip -s route show cache 209.85.229.99
209.85.229.99 from 192.168.0.165 via 192.168.0.200 dev eth0
    cache  users 1 age 16sec mtu 1500 advmss 1460 hoplimit 64
209.85.229.99 via 192.168.0.200 dev eth0  src 192.168.0.165
    cache  users 1 used 2 age 15sec mtu 1500 advmss 1460 hoplimit 64

With no expires on and from my experiments if I keep up a simple ping then
the route is retained.

However the following route:

atom3:~# ip -s route show cache 92.63.131.67
92.63.131.67 from 10.50.0.1 via 10.50.0.2 dev tun0
    cache  users 1 used 103 age 1sec mtu 1500 advmss 1460 hoplimit 64
92.63.131.67 via 10.50.0.2 dev tun0  src 10.50.0.1
    cache  expires 79sec users 1 used 209 age 1sec mtu 1480 advmss 1460
hoplimit 64

has an expires time and when it expires it can get thrown over to the other
connection (which would disconnect any open sessions that check IP
consistency...)

This seems to be the case depending on which gateway is being used. You'll
notice that the second link is via a tunnel.

Is there any way of controlling the expires behaviour or even finding out
why it gets set so I can find a mitigating measure? I can post more details
about the network as it is purely a test bed at this point - its fairly
complex so I didn't want to post a load of irrelevant information....

Thanks in advance,
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