Re: 2 default gateway on two diffrent nic

Hi,

Just a question. How are you going to go about doing NAT for the 2
lines since the webserver inbound traffic is coming from the 2
different lines?

On 8/18/05, Rainer Nagel <rainer.nagel@freenet-rz.de> wrote:
> 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
> WillstätterStr. 13, D-40549 Düsseldorf Tel.: +49 211 53087 423
> Vorstand: Eckhard Spoerr (Vors.), Fax.: +49 211 53087 500
> Axel Krieger, Stephan Esch, Eric Berger Amtsgericht Hamburg
> Vorsitzender des Aufsichtsrates: Prof. Dr. Helmut Thoma HRB 74048
>
>
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