42-89
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 42 Configuring IP Unicast Routing Configuring Unicast Reverse Path Forwarding
For more information about the information in the displays, see the Cisco IOS Switching Services
Command Reference, Release 12.2.
Configuring Unicast Reverse Path Forwarding
The unicast reverse path forwarding (unicast RPF) feature helps to mitigate problems that are caused by
the introduction of malformed or forged (spoofed) IP source addresses into a network by discarding IP
packets that lack a verifiable IP source address. For example, a number of common types of
denial-of-service (DoS) attacks, including Smurf and Tribal Flood Network (TFN), can take advantage
of forged or rapidly changing source IP addresses to allow attackers to thwart efforts to locate or filter
the attacks. For Internet service providers (ISPs) that provide public access, Unicast RPF deflects such
attacks by forwarding only packets that have source addresses that are valid and consistent with the IP
routing table. This action protects the network of the ISP, its customer, and the rest of the Internet.
Note Do not configure unicast RPF if the switch is in a mixed hardware stack combining more than one switch
type: Catalyst 3750-X, Catalyst 3750-E, and Catalyst 3750 switches.
For detailed IP unicast RPF configuration information, see the Other Security Features chapter in the
Cisco IOS Security Configuration Guide, Release 12.2 at this URL:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configuration_guide_book09186a
0080087df1.html
Configuring Protocol-Independent Features
This section describes how to configure IP routing protocol-independent features. These features are
available on switches running the IP base or the IP services feature set; except that with the IP base
feature set, protocol-related features are available only for RIP. For a complete description of the IP
routing protocol-independent commands in this chapter, see the “IP Routing Protocol-Independent
Commands” chapter of the Cisco IOS IP Command Reference, Volume 2 of 3: Routing Protocols,
Release 12.2.
• Configuring Distributed Cisco Express Forwarding, page 42-89
• Configuring the Number of Equal-Cost Routing Paths, page 42-91
• Configuring Static Unicast Routes, page 42-92
• Specifying Default Routes and Networks, page 42-93
• Using Route Maps to Redistribute Routing Information, page 42-93
• Configuring Policy-Based Routing, page 42-97
• Filtering Routing Information, page 42-100
• Managing Authentication Keys, page 42-103

Configuring Distributed 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