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Linux router with 2 WAN, 1LAN, iproute2

Link to this post 30 Jun 11

Hi,

I would like to build a linux router using Ubuntu 11.4 which i have installed on a pc with 3 ethernet interfaces which are assigned like so:

eth0 - LAN -> IP: 192.168.3.1
eth1 - WAN1 -> IP: 192.168.2.146
eth2 - WAN2 -> IP: 91.212.254.117

I want my router to use both WAN connections and when one of them goes down to keep working unintererupted on the other one.
For the purpose of testing my setup i am using the internet on the router itself, trying to ping the gateways on each WAN. This is my setup:

root@rlite:/home/sysop/router# ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN qlen 1000
link/ether 00:30:18:4a:ef:06 brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:30:18:4a:ef:05 brd ff:ff:ff:ff:ff:ff
4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:30:18:4a:ef:04 brd ff:ff:ff:ff:ff:ff
root@rlite:/home/sysop/router# ip route list
91.212.254.64/26 dev eth2 proto kernel scope link src 91.212.254.117
192.168.3.0/24 dev eth0 proto kernel scope link src 192.168.3.1
192.168.2.0/24 dev eth1 proto kernel scope link src 192.168.2.146
default
nexthop via 91.212.254.65 dev eth2 weight 1
nexthop via 192.168.2.1 dev eth1 weight 1
root@rlite:/home/sysop/router# ip rule
0: from all lookup local
32764: from 91.212.254.117 lookup 202
32765: from 192.168.2.146 lookup 201
32766: from all lookup main
32767: from all lookup default
root@rlite:/home/sysop/router# ip route list table 201
192.168.2.0/24 dev eth1 scope link src 192.168.2.146
default via 192.168.2.1 dev eth1
root@rlite:/home/sysop/router# ip route list table 202
91.212.254.64/26 dev eth2 scope link src 91.212.254.117
default via 91.212.254.65 dev eth2


Now for my problem...
I start by pinging some IP in the internet. I check the route to that ip

ip route get 8.8.8.8

...and discover it's going out through eth2. I unplug the cable from eth2 and the ping keeps getting replys. Checking the route again reveals that the route is nou going through eth1 which is just fine. I put back the cable into eth2 and unplug it from eth1. Route switches back to eth2. Problem is that when i put the cable back into eth1 i start getting erros ( destination host not found ) and it takes verry long for it to start getting replys again. Also if i unplug the cable from eth2 while pinging eth2 gw and then plug it back again it just works seemlesly but if i do the same with eth1 i have to wait a lot of time for the thing to start getting replys again and first i get some destination host not found errors. This dosn't happen with eth2. So how can i make my router work propperly and track down the problem ?

Link to this post 07 Jul 11

eth2 is the only one with a external IP Address, you currently have 1 WAN and 2 LANs.

Link to this post 07 Jul 11

The ip 192.168.2.1 is also a gateway inside of my lan. Anyway, problem solved. I wrote a small script that pings the gateways and changes the default route and it works well.

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