On Wednesday, January 08, 2014 10:33:55 PM joel jaeggli wrote:
There are various reasons why one might take a full table on a switch with not not enough FIB, the important part of course being the part where you don't install them all.
In Metro-E deployments, this is a good use-case when the box is providing both IP and Ethernet services to the same or different customers out of the same chassis. It avoids having to run 2x eBGP sessions for the IP services (the first being point-to-point eBGP between the switch and the customer to get their routes into the network, and the second being an eBGP Multi-Hop between the customer and a "bigger" box in your core to send them the full BGP table). If a switch allows you to keep the routes in control plane RAM without downloading them into the FIB, you can maintain a single point-to-point eBGP session to the customer, including sending them the full table, provided you have a default route in the switch's FIB to handle actual data plane traffic flow from the customer upstream. Mark.