906
Configuring IP Unicast Routing
Configuring Protocol-Independent Features
Configuring Protocol-Independent Features
This section describes how to configure IP routing protocol-independent features. For a complete description of the IP
routing protocol-independent commands in this chapter, see the Cisco IOS IP Routing: Protocol-Independent Command
Reference.
This section includes the following topics:
Configuring Cisco Express Forwarding, page 906
Configuring the Number of Equal-Cost Routing Paths, page 908
Configuring Static Unicast Routes, page 908
Specifying Default Routes and Networks, page 910
Using Route Maps to Redistribute Routing Information, page 911
Configuring Policy-Based Routing, page 915
Filtering Routing Information, page 919
Managing Authentication Keys, page 922
Configuring Cisco Express Forwarding
Cisco Express Forwarding (CEF) is a Layer 3 IP switching technology used to optimize network performance. CEF
implements an advanced IP look-up and forwarding algorithm to deliver maximum Layer 3 switching performance. CEF
is less CPU-intensive than fast switching route caching, allowing more CPU processing power to be dedicated to packet
forwarding. In dynamic networks, fast switching cache entries are frequently invalidated because of routing changes,
which can cause traffic to be process switched using the routing table, instead of fast switched using the route cache.
CEF uses the Forwarding Information Base (FIB) lookup table to perform destination-based switching of IP packets.
The two main components in CEF are the distributed FIB and the distributed adjacency tables.
The FIB is similar to a routing table or information base and maintains a mirror image of the forwarding information
in the IP routing table. When routing or topology changes occur in the network, the IP routing table is updated, and
those changes are reflected in the FIB. The FIB maintains next-hop address information based on the information in
the IP routing table. Because the FIB contains all known routes that exist in the routing table, CEF eliminates route
cache maintenance, is more efficient for switching traffic, and is not affected by traffic patterns.
Nodes in the network are said to be adjacent if they can reach each other with a single hop across a link layer. CEF
uses adjacency tables to prepend Layer 2 addressing information. The adjacency table maintains Layer 2 next-hop
addresses for all FIB entries.
Because the switch uses Application Specific Integrated Circuits (ASICs) to achieve Gigabit-speed line rate IP traffic,
CEF forwarding applies only to the software-forwarding path, that is, traffic that is forwarded by the CPU.
Command Purpose
show ip protocols vrf vrf-name Display routing protocol information associated
with a VRF.
show ip route vrf vrf-name [connected] [protocol [as-number]]
[list] [mobile] [odr] [profile] [static] [summary] [supernets-only]
Display IP routing table information associated
with a VRF.
show ip vrf [brief | detail | interfaces] [vrf-name] Display information about the defined VRF
instances.
To Next Page
Loading...
Need help?
General
