Hi Abraham, Thanks for the response. I should have mentioned that we are running OSPF. If I'm not mistaken (and please correct me if I am!) you are suggesting how we might configure the policy routing in R1. We got this far ourselves, but the difficulty arises when one of our links (to B or C - which I should mention again are in fact the same destination ultimately) goes down. The policy routing in R1 necessarily over-rides OSPF (or OSPF would have it's way with all traffic, and send it down one link or the other - or perhaps load balance. We wouldn't be able to route on the basis of packet characteristics.) So the traffic gets sent from R1 to, say R3, even though the link from R3 to C is broken. R3 must then re-route the traffic out via R2. This happens, but it is being sent back down the sub-interface it arrived at, which, I believe, contravenes an RFC, and risks setting up a routing loop. I wondered if anyone knew how or why we are seeing this, since it really should not be happening, and I'm concerned that it might stop happening under different circumstances! I think my subject line might be misleading as the policy routing itself is not the problem. Thanks, James > Create two routing tables for link B and link C. Add default > gateways in > these tables for each link (and routes to your network if you > use static > routing to route packets to R2/R3) > > then add rules to enqueue packets destined for your network > into the main > table. then add rules to enqueue packets originating from > your network to > those tables. > > the dynamic routes are sent to the main table (which have the lowest > priority). > > so you have > > ip rule add to $net_a table main pref 50 > ip rule add to $net_b table main pref 60 > ip rule add from $net_a table $table_a pref 70 > ip rule add from $net_b table $table_b pref 80 > ip route add default via $gw_a table $table_a > ip route add default via $gw_b table $table_b > (extra static routes if you don't use dynamic routing within > you network) > > the rest gets added by zebra/gated/whatever you use for > dynamic routing. > > > > > > > R2 ---- B > > / > > / > > / > > ---> A --- R1 > > \ > > \ > > \ > > R3 ---- C > > > > The Information contained in this E-Mail and any subsequent correspondence is private and is intended solely for the intended recipient(s). For those other than the recipient any disclosure, copying, distribution, or any action taken or omitted to be taken in reliance on such information is prohibited and may be unlawful.
