Re: [lvs-users] LVS-DR + 2 pools in 2 networks = hair pulling

To: David Coulson <david@xxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] LVS-DR + 2 pools in 2 networks = hair pulling
Cc: " users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
From: tom <tg01@xxxxxxxxxx>
Date: Sun, 29 Apr 2012 04:55:47 +1000

> Have you tried disabling reverse path filtering?
> echo 0 > /proc/sys/net/conf/eth0/rp_filter

Spot on! This was the issue.

I set up rp_filter (I didn't know this parameter before your answer) to 
be 'loose'. Indeed in my case the packet was silently dropped because a 
packet coming from 123.2.2 was coming on eth1 being the 10.1.1 network. 
And because eth0 was 123.2.2, the kernel thought "Wait a minute a packet 
from 123.2.2 should be seen on eth0, not eth1! This does not look right, 
I am going to, silently, drop it !". Being "loose", echo 2 > 
/proc/sys/net/conf/eth1/rp_filter allows any networks on the server to 
be allowed to arrive on eth1. So eth0's network is ok to be seen on 
eth1. Disabling rp_filter (echo 0) allows anything, which would work as 
well but the loose option (echo 2) is more conservative without being 
too much of a nazi :)

Anyway, thanks a lot David for pointing that out !


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