Routing on an Ubuntu bridge

How do you add routes on ubuntu?

Please see the link below:

http://www.comptechdoc.org/os/linux/usersguide/linux_ugrouting.html

Thats helpful, but here's the problem: The network connected to the 3rd NIC is public, and if I put a static route on it, then all traffic to that network will go out that way. I want that traffic to go out the bridge. I just want SSH to work on it.

The static route you want to add should be to your pc.

There will be more than one PC connecting to it from dynamic IPs. Here is a rough Visio drawing that might help: <a href="http://www.tharo.com/network.jpg">http://www.tharo.com/network.jpg</a>

I looked at your diagram, and

- your two interfaces that are used for squid are: 192.168.5.1 and 192.168.5.2
- the interface that you are welling to use for ssh is 192.168.4.2 going through FW (is it natted to 1.2.3.174?)
- you have two internet links
- you want to ssh from any where to 3rd interface

It seems that when traffic comes to this interface you do not allow it to go back through 192.168.5.0. Is this correct (since there is no default gateway on the 3rd interface)?

you need to allow this (on your firewall / iptables)

1. Please provide the details.

eth0 -> IP? -> External Squid ?
eth1 -> IP? -> Internal Squid ?
eth2 -> IP? -> External ssh admin ?

2. Do you have any firewall running on the Linux box ?

The Squid box does not have any firewall setup on it. eth0 and eth1 are bridged and have an IP of 192.168.5.25. eth2 is 192.168.4.2. I don't want any Internal traffic to go out eth2. It's only for SSH from the outside. If I set a Default GW, ALL internal traffic goes out eth2, even though there is a gateway set for the bridge to 192.168.5.1

You will need to setup policy routing.

Standard Linux has 3 tables  local, main, and default.

The trick is to split the 2 default GW's into 2 routing tables and then use routing rules to select the correct one.

see  # ip rule show

 1. Add normal default route out the bridged interface.
#ip route add default via GWeth1
>>This will end up in main

2. Add default gw out ssh eth2 with
#ip rule add from 192.168.4.2 priority 1000 table 100
then add the default GW
ip route add default via GWeth2 table 100

The rule at 1000 will select the 100 routing table before main if the packet has a source ip of 192.168.4.2

OK, let me make sure I'm clear here before I go messing up my routing tables. I should type the following?

ip route add default via 192.168.5.25    #(This is the IP of the bridge interface. Or should this be the next hop?)
ip rule add from 192.168.4.2 priority 1000 table 100
ip route add default via 192.168.4.2 table 100   #(Again, this is the interface IP, not the gateway IP?)

Thanks a million!

Perfect! It's exactly what I needed. Thank you!