Packet Forwarding #
CEF: Cisco Proprietary, used in general CPU platforms and ASIC’s with NPU’s
TCAM: Ternary Content Addressable Memory allows for upper layer processing Layer2/3 source/destination addresses, Protocol, QoS Markings, Etc. it can provide a true, false, or do not care result (ternary)
Centralized forwarding is when a route process engine is equipped with a forwarding engine.
Distributed forwarding the local forwarding engine will send information about he pack to the forwarding engine the route process engine / switch fabric maybe invoked if the egress port is on another switch / line card
Software CEF holds the forwarding information base (FIB) and Adjacency Table / a Information Base(AIB). The FIB is a copy of the routing table and the Adjacency table keeps next-hop information. Packets will be rate-limited if processed by the CPU and have an incomplete adjacency table TTL is a loop-prevention mechanism
When using SDM template every switch must use the same template which for the Cat 9k there are 2 commands
Conf t
Sdm prefer (vlan|advance)