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Software Configuration Guide—Release 12.2(25)SG
OL-7659-03
Chapter1 Product Overview
Layer 3 Software Features
Policy-Based Routing, page 1-9
Unidirectional Link Routing, page 1-9
VRF-lite, page 1-9
CEF
Cisco Express Forwarding (CEF) is an advanced Layer 3 IP-switching technology. CEF optimizes
network performance and scalability in networks with large and dynamic traffic patterns, such as the
Internet, and on networks that use intensive web-based applications o r interactive sessions. Although
you can use CEF in any part of a network, it is designed for high-performance, highly resilient Layer 3
IP-backbone switching.
For information on configuring CEF, see Chapter 23, “Configuring Cisco Express Forwarding.”
HSRP
The Hot Standby Router Protocol (HSRP) provides high network availability by routing IP traffic from
hosts on Ethernet networks without relying on the availability of any single Layer 3 switch. This feature
is particularly useful for hosts that do not support a router di scovery protocol and do not have the
functionality to switch to a new router when their selected router reloads or loses power.
For information on configuring HSRP, refer to the following URL:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/ip_c/ipcprt1/1cdip.htm
IP Routing Protocols
The following routing protocols are supported on the Catalyst 4500 series switch:
RIP
OSPF
IS-IS
IGRP
EIGRP
BGP

RIP

The Routing Information Protocol (RIP) is a distance-vector, intradoma in routing protocol. RIP works
well in small, homogeneous networks. In large, complex internetworks, it has many limitations, such as
a maximum hop count of 15, lack of support for variable-leng th subnet masks (VLSMs), inefficient use
of bandwidth, and slow convergence. RIP II does support VLSMs.

OSPF

The Open Shortest Path First (OSPF) protocol is a standards-based IP routing protocol designed to
overcome the limitations of RIP. Because OSPF is a link-state routing protocol, it sends link-state
advertisements (LSAs) to all other routers within the same hierarchical ar ea. Information on the attached