Which two statements about Cisco Express Forwarding are true? (Choose two.)
A.
Cisco Express Forwarding tables contain reachability information and adjacency tables contain
forwarding information.
B.
Cisco Express Forwarding tables contain forwarding information and adjacency tables contain
reachability information.
C.
Changing MAC header rewrite strings requires cache validation.
D.
Adjacency tables and Cisco Express Forwarding tables can be built separately.
E.
Adjacency tables and Cisco Express Forwarding tables require packet process-switching.
Main Components of CEF
Information conventionally stored in a route cache is stored in several data structures for Cisco
Express Forwarding switching. The data structures provide optimized lookup for efficient packet
forwarding. The two main components of Cisco Express Forwarding operation are the forwarding
information base (FIB) and the adjacency tables.
The FIB is conceptually similar to a routing table or information base. A router uses this lookup
table to make destination-based switching decisions during Cisco Express Forwarding operation.
The FIB is updated when changes occur in the network and contains all routes known at the time.
Adjacency tables maintain Layer 2 next-hop addresses for all FIB entries.
This separation of the reachability information (in the Cisco Express Forwarding table) and the
forwarding information (in the adjacency table), provides a number of benefits:
Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipswitch_cef/configuration/15-mt/iswcef-
15-mt-book/isw-cef-overview.html
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