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V-237749

CAT II (Medium)

The Cisco switch must be configured to have Cisco Express Forwarding enabled.

Rule ID

SV-237749r648775_rule

STIG

Cisco IOS Switch RTR Security Technical Implementation Guide

Version

V3R3

CCIs

CCI-000366

Discussion

The Cisco Express Forwarding (CEF) switching mode replaces the traditional Cisco routing cache with a data structure that mirrors the entire system routing table. Because there is no need to build cache entries when traffic starts arriving for new destinations, CEF behaves more predictably when presented with large volumes of traffic addressed to many destinations such as a SYN flood attacks that. Because many SYN flood attacks use randomized source addresses to which the hosts under attack will reply to, there can be a substantial amount of traffic for a large number of destinations that the switch will have to handle. Consequently, switches configured for CEF will perform better under SYN floods directed at hosts inside the network than switches using the traditional cache.

Check Content

Review the switch to verify that CEF is enabled.

IPv4 Example: ip cef 
IPv6 Example: ipv6 cef 

If the switch is not configured to have CEF enabled, this is a finding.

Fix Text

Enable CEF

IPv4 Example: ip cef 
IPv6 Example: ipv6 cef