The Cisco PE switch must be configured with Unicast Reverse Path Forwarding (uRPF) loose mode enabled on all CE-facing interfaces.
An XCCDF Rule
Description
<VulnDiscussion>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.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>
- ID
- SV-220456r622190_rule
- Severity
- Medium
- References
- Updated
Remediation - Manual Procedure
Configure uRPF loose mode on all CE-facing interfaces as shown in the example below:
SW2(config)#int SW1(config)#int g0/2
SW2(config-if)#ip verify unicast source reachable-via any
SW2(config-if)#end