[Novalug] multihomed linux router with public ip addresses

Nick Danger nick@hackermonkey.com
Tue Apr 27 11:50:33 EDT 2010


On 04/27/2010 10:25 AM, Miguel González Castaños wrote:

> But how? If you use two IPs of the same subnet in the linux router, you 
> get two routes in the routing table for that subnet that are forwarded 
> to different interfaces. It's what I said in my first message. Let's say
> 
> eth2 - 80.35.2.3 - facing to the Internet
> 
> eth0  - 10.30.1.1
> 
> eth1 - 80.35.2.2
> 
> if you run netstat -rn you get two routes for 80.35.2.0 that are routed 
> to eth2 and eth1

 You CAN have two interfaces in the same network. IE:

[me@chimay ~]$ netstat -rn
Kernel IP routing table
Destination    Gateway   Genmask        Flags     MSS Window rtt iface
xxx.yyy.64.0   0.0.0.0   255.255.255.0  U         0 0        0   eth0
xxx.yyy.64.0   0.0.0.0   255.255.255.0  U         0 0        0   eth1
169.254.0.0    0.0.0.0   255.255.0.0    U         0 0        0   eth1
0.0.0.0        xxx.yyy.64.1  0.0.0.0    UG        0 0        0   eth0
[me@chimay ~]$

Packets by default head out the lowest interface, eth0. I have a few
rulesets to force some out eth1. And some very complicated iptables rules.

Nick



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