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Re: LVS-TUN gets stuck on one realserver

To: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re: LVS-TUN gets stuck on one realserver
From: Todd Lyons <tlyons@xxxxxxxxxx>
Date: Tue, 30 Nov 2004 16:18:11 -0800
Daniil Sosonkin wanted us to know:

>Hi all,
>
>I'm very new to LVS but managed to configure it on Mandrake 10 (kernel 
>2.6.3-7mdksmp, had precompiled IP Virtual Server version 1.1.8 

On the real servers, do you have the following:
/proc/sys/net/ipv4/conf/lo/arp_ignore
/proc/sys/net/ipv4/conf/lo/arp_announce
/proc/sys/net/ipv4/conf/all/arp_ignore
/proc/sys/net/ipv4/conf/all/arp_announce

Probably not, here's what's on my 2.6.3 (Mandrake 10.0) kernel:

[root@trip root]# uname -r
2.6.3-16mdk
[root@trip root]# sysctl -a | grep arp_
net.ipv4.conf.eth0.arp_filter = 0
net.ipv4.conf.tun0.arp_filter = 0
net.ipv4.conf.lo.arp_filter = 0
net.ipv4.conf.default.arp_filter = 0
net.ipv4.conf.all.arp_filter = 0

The following URL addresses the issue with your kernel version and
overall, that chapter explains the arp problem very clearly:
http://www.austintek.com/LVS/LVS-HOWTO/HOWTO/LVS-HOWTO.arp_problem.html#2.6_arp

That section explains a few solutions as well, whether you think they're
clear or not will be your judgement.  In summary, this fixed the problem
for me on the real servers:

smtp1 root # tail -6 /etc/sysctl.conf 
# For load balanced machines
net.ipv4.conf.lo.arp_ignore = 1
net.ipv4.conf.lo.arp_announce = 2
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2

Caveat: I'm doing LVS-DR, not LVS-TUN.  I don't know if it will do
anything for you.  I've never messed with the TUN side of things.
-- 
Regards...              Todd
They that can give up essential liberty to obtain a little temporary 
safety deserve neither liberty nor safety.       --Benjamin Franklin
Linux kernel 2.6.8.1-12mdkenterprise   2 users,  load average: 0.00, 0.03, 0.02

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