Re: [lvs-users] Error on lo after adding IP

To: " users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] Error on lo after adding IP
From: "L.S. Keijser" <leon@xxxxxxxx>
Date: Mon, 26 Apr 2010 06:51:26 +0200
On Fri, 2010-04-23 at 16:25 -0700, Gary Smith wrote:
> I added a new alias to lo
> /etc/sysconfig/networks-scripts/ifcfg-lo:0
> DEVICE=lo:0
> When I issue service network restart I get:
> Bringing up loopback interface:  SIOCADDRT: Network is unreachable
> Running ip addr I get the addresses expected.  Should I be concerned about 
> this?  Is there something I need to do differently to the alias file that I'm 
> missing?

Don't use the network-scripts file to configure the loopback adapter. It
will send out an unwanted arp broadcast to determine if the address is
already in use (in the case of LVS-DR, it probably is) and refuse to
come up. Also, the arp table on other nodes will be incorrect since the
MAC address associated with the VIP should only exist for the interface
configured on the director. 

Configure the loopback device by putting these lines in
your /etc/rc.local file :

# solve the ARP problem
echo 1 > /proc/sys/net/ipv4/conf/lo/arp_ignore
echo 1 > /proc/sys/net/ipv4/conf/eth0/arp_ignore
echo 2 > /proc/sys/net/ipv4/conf/lo/arp_announce
echo 2 > /proc/sys/net/ipv4/conf/eth0/arp_announce

# Bring up loopback interface
ifconfig lo:0 broadcast netmask 0xffffffff

You can check if you configured it correctly by doing an 'arping VIP'
from a client (not the director / realserver!) and watching the output.
You should see replies coming from one MAC address. This would be the
MAC of the interface on the director that's serving the VIP.

(i should really make a template from this mail ...)


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