Hi Jean-Philippe,
On Wed, Aug 17, 2005 at 08:36:22PM +0200, Jean-Philippe Egger wrote:
> I've been trying to set up a full redundant web system using loadbalancing
> technics (ultramonkey). To incorporate a redundancy in the network itself
> (in case a switch fails) each machine behind the loadbalancer has two
> internal nics on two diffrent networks.
>
>
> (external ip)
> eth0
> loadbalancer
> eth1 eth2
> 192.168.7.2 192.168.8.2
> ¦ ¦
> ¦ ¦
> ¦ ¦
> 192.168.7.4 192.168.8.4
> eth0 eth1
> webserver1
>
> default gateway for eth0 (webserver1) is 192.168.7.2
> default gateway for eth1 (webserver1) is 192.168.8.2
>
>
> My problem is the following:
>
> I set up load balancing which works fine when only one nic is up on the web
> server. I can ping -I eth0 www.google.com or ping -I eth1 www.google.com
> respectevely when eth0 or eth1 is up. The problems start when both cards are
> up. I can only ping with one interface outside of the local net (local pings
> works on both nics). It is always the last card ifup'ed that can ping. If I
> don't specify the interface while pinging it works fine using the last
> ifup'ed interface. My biggest problem is that the load balancer thinks both
> nics are up and that the service is available on both, thus every second
> time i get no response from the web server.
>
> I'm pretty shure this has to do with having two gateways for a single
> machine. When I remove the default route of the first card (the one that
> works) I can suddenly ping the outside world on the second card.
Use policy routing to tie a default route to any ip.
Install iproute, add two table names to /etc/iproute2/rt_tables and set
rules for both ips:
ip rule add from 192.168.7.4 table eth0
ip rule add from 192.168.8.4 table eth1
Than add two default routes:
ip route add default via 192.168.7.2 dev eth0 table eth0
ip route add default via 192.168.8.2 dev eth1 table eth1
Ciao
--
Rainer Nagel, freenet.de AG Rainer.Nagel@freenet-rz.de
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