At 8:11 PM +0000 9/4/02, richard dumoulin wrote: >Thx but I already knew that. I am just having difficulties in understanding >their functions. What are they for ? >
While small routers may only have a RIB, a router with any real performance has both -- it may even have multiple FIBs. The RIB is what you see when you show ip route. It is a memory area that is structured not for fast lookup in forwarding, but for ease of updating with new routes. It's often structured as some kind of linked list/tree. The FIB may be implemented in software or hardware. You can display it with various show cache commands. It is designed for very fast lookup of destinations and associated output interfaces while actually forwarding packets. Typically, it's structured as some sort of hash table. In dCEF, there are multiple copies of the FIB in each VIP. Some kinds of FIBs contain only a subset of the routes known to the RIB, and updating them selectively versus deleting and rebuilding them from the RIB is a challenge. In CEF, there is a one-to-one correspondence between RIB and FIB entries, so the "cache miss" problem never happens. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=52704&t=52681 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
