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


Finding ID Version Rule ID IA Controls Severity
V-237750 CISC-RT-000235 SV-237750r648776_rule Medium
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.
Cisco IOS XE Switch RTR Security Technical Implementation Guide 2023-09-13


Check Text ( C-40969r648773_chk )
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 (F-40931r648774_fix)
Enable CEF

IPv4 Example: ip cef
IPv6 Example: ipv6 cef