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V-221127

CAT II (Medium)

The Cisco PE switch must be configured with Unicast Reverse Path Forwarding (uRPF) loose mode enabled on all CE-facing interfaces.

Rule ID

SV-221127r999736_rule

STIG

Cisco NX OS Switch RTR Security Technical Implementation Guide

Version

V3R4

CCIs

CCI-001097

Discussion

The uRPF feature is a defense against spoofing and denial-of-service (DoS) attacks by verifying if the source address of any ingress packet is reachable. To mitigate attacks that rely on forged source addresses, all provider edge switches must enable uRPF loose mode to guarantee that all packets received from a CE switch contain source addresses that are in the route table.

Check Content

Review the switch configuration to determine if uRPF loose mode is enabled on all CE-facing interfaces.

interface Ethernet1/2
 ip address x.1.12.2/30
 ip access-group BLOCK_TO_CORE in
 ip verify unicast source reachable-via any

If uRPF loose mode is not enabled on all CE-facing interfaces, this is a finding.

Fix Text

Configure uRPF loose mode on all CE-facing interfaces as shown in the example below:

SW1(config)# int e1/2
SW1(config-if)# ip verify unicast source reachable-via any
SW1(config-if)# end