[TriLUG] Routing traffic to a non-default gateway

[Brian via TriLUG]

On 1/11/23 09:06, Mauricio Tavares via TriLUG wrote:
> I have a linux host, bob, acting as a router. Traffic goes out using
> its default gateway, 192.168.1.1/24 interface br-out. So far so good.
> 
> I have two networks I would like to focus on:
> - 192.168.10.0/24, interface br-closed. bob is also acting as dhcp/dns
> for this network.
> - 192.168.2.0/30 (hop to other router, whose IP is 192.168.2.2),
> interface br-hop
> 
> I want to have all devices in br-closed to use br-hop as their default
> gateway, and I seem to be having a hard time writing the proper ip
> route statement for that. Or maybe I should use iptables instead,
> which leads to: what is the best way and why?

I think this can be accomplished by having bob configure the clients on 
br-closed to use 192.168.2.2 as /their/ default gateway via dhcp (dhcp 
option 3).  It will also be necessary to send them a static route so 
that they know 192.168.2.0/30 is accessible via bob's .10.0/24 address 
(dhcp option 121)

I think that'll do the trick.  bob himself only needs to know routing is 
allowed between those two interfaces.

HTH,
-Brian