Identify Cisco express forwarding (CEF) concepts

CEF made of

CEF enabled by default IOS 12.0 or later

Types
centralized  CEFF
RP make the EF

How to check

 #ip cef  

Distributed CEF on catalyst 6500

Line Cards make the EF
Configure
#IP cef distributed.
Distributed CEF uses an interprocess communication (IPC) to ensure
synchronization of FIB tables and AdjTables on the RP and Line cards

CEF Support

ATM/AAL5snap, ATM/AAL5mux, and ATM/AAL5nlpid
Ethernet
FDDI
Frame Relay
High-Level Data Link Control (HDLC)
PPP
Spatial Reuse Protocol (SRP)
TokenRing
Tunnels

FIB contains all routes
Adjancency table  all L2 next hops for all FIB entries


CEF features enabled by Default.
Per-destination LB
Distributed Tunnel Switching
MUltipoint GRE


RIB Router Information Base this is the routing table itself
A router may have many separate RIB’s. If you’re running vrfs  then each vrf will have a separate RIB

FIB
The FIB is a mirror image of the IP routing table,Changes to the routing table and next hop ip’s are reflected in the FIB.

LIB
The LIB is an MPLS table. This is the place where the router will keep all known MPLS label

 #sh mpls ldp bindings  

LFIB – Label Forwarding Instance Base
Its the table used to forward labeled packets. It is populated with the incoming and outgoing labels for the LSP
As the RIB uses the FIB to forward traffic, so the LIB uses the LFIB to forward traffic

 #sh mpls forwarding-table  

The adjacency table is populated with l2 next hop addresses for all FIB entries, hence adjacency. When an adjacency is established,
as through ARP, a link layer header for that adjacency is stored in the adjacency table.

Configure

 #ip load-sharing per-packet  

Adjacency Type

Null Adjacency pkts destined to a null0 interface
Glean Adjacency packets destined to a multiaccess medium, Next hop should be directly connected
                but there is no MAc header rewrite information available, when needed CEF request ARP entries for a specific preix
Punt Adjacency  Fwd pkts require special handling,or not supported with CeF to the next higher switching level.(RP)
Discard Adjacency
Drop Adjacency

How to check

 #show ip cef  
 #show adjacency s0/0 detail