[clug] A Routing problem
rod at tpgi.com.au
Wed Oct 20 22:49:57 GMT 2004
thats no problem. You setup different routing tables based on source
address/device. This way each interface can see a completely different
set of routes. We have a router here with 6 ethernet interfaces of
which 2 are feeds out of the building used for different purposes.
Routing is done based on both source and dest addresses.
Here's a quick cut and paste example :-
# specify anything from 192.168.76.0/24 uses the new table called privateip
ip rule add from 192.168.76.0/24 table privateip
#Set up the routes for this table.
ip route add default via 192.168.99.1 dev eth5 table privateip
ip route add 192.168.76.0/26 dev eth4 src 192.168.76.1 table privateip
ip route add 192.168.76.208/28 via 192.168.0.2 dev eth2 table privateip
ip route add 192.168.76.192/28 dev eth3 src 192.168.76.193 table privateip
<snip> and so on.
You need to create the new table entry (ie 501) and optionally give it a
name for each routing table you need. In your case three tables may be
overkill but it gives you the most flexability if your networks are
perpetually in a state of flux (like ours)
We had some issues with arp due to our rather weird lan setup and found
echo 1 > /proc/sys/net/ipv4/conf/all/arp_filter was needed as well. YMMV
Very low end hardware will cope with this kind of set up no problems at
all. Our 6 port box is a PIII with 4 x 100M lans and 2 x 2M+ feeds out
of the building and doesnt raise a sweat. Gotta love linux routers!
The linux advanced routing & traffic control howto covers this quite well.
(from next door)
This email may contain traces of nuts and/or caffeine
Stephen Hodgman wrote:
> I have a question regarding routing. I have a linux system with three
> interfaces say eth0, eth1 & eth2
> On eth0 is network 22.214.171.124/24 (say)
> I want traffic entering eth1, destined for 126.96.36.199/24 to be routed
> to eth0 - always
> I want traffic entering from eth2 destined for 188.8.131.52/24 to be
> routed to eth2 - always
> The reason is that there is a route either way but I only want one
> device to route directly.
> Can this be done? It seems to require routing tables based on source
> I would appreciate knowing how this can be done.
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