The Cisco PE switch providing MPLS Layer 2 Virtual Private Network (L2VPN) services must be configured to authenticate targeted Label Distribution Protocol (LDP) sessions used to exchange virtual circuit (VC) information using a FIPS-approved message authentication code algorithm.

An XCCDF Rule

Description

<VulnDiscussion>LDP provides the signaling required for setting up and tearing down pseudowires (virtual circuits used to transport Layer 2 frames) across an MPLS IP core network. Using a targeted LDP session, each PE switch advertises a virtual circuit label mapping that is used as part of the label stack imposed on the frames by the ingress PE switch during packet forwarding. Authentication provides protection against spoofed TCP segments that can be introduced into the LDP sessions.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>

ID: SV-221120r856631_rule
Severity: Medium
References: CCI-001958
Updated: 8 months ago

The severity level can be downgraded to a category 3 if the switch is configured to authenticate targeted LDP sessions using MD5 as shown in the example below:

Step 1: Configure a key chain for LDP sessions.

 SW1(config)# key chain LDP_KEY
SW1(config-keychain)# key 1SW1(config-keychain-key)# key-string xxxxxxxxxxxx
SW1(config-keychain-key)# send-lifetime 00:00:00 Oct 1 2019 23:59:59 Dec 31 2019
SW1(config-keychain-key)# accept-lifetime 00:00:00 Oct 1 2019 01:05:00 Jan 1 2020
SW1(config-keychain-key)# exit
SW1(config-keychain)# exit

Step 2: Configure a prefix lists to identify LDP neighbors.

SW1(config)# ip prefix-list LDP_NBR1 permit 10.1.22.2/32
SW1(config)# ip prefix-list LDP_NBR2 permit 10.1.12.4/32

Step 3: Apply the key chain to the LDP neighbors.

SW1 (config)# mpls ldp configurations
SW1 (config-ldp)# password required for LDP_NBR1
SW1 (config-ldp)# password option 1 for LDP_NBR1 key-chain LDP_KEY
SW1 (config-ldp)# password required for LDP_NBR2
SW1 (config-ldp)# password option 1 for LDP_NBR2 key-chain LDP_KEY
SW1 (config-ldp)# end

The Cisco PE switch providing MPLS Layer 2 Virtual Private Network (L2VPN) services must be configured to authenticate targeted Label Distribution Protocol (LDP) sessions used to exchange virtual circuit (VC) information using a FIPS-approved message authentication code algorithm.

Description

Remediation - Manual Procedure