Title

The Cisco ACI must be configured to advertise a hop limit of at least 32 in Cisco ACI Advertisement messages for IPv6 stateless auto-configuration deployments. (Cat III impact)

Discussion

The Neighbor Discovery Protocol allows a hop limit value to be advertised by routers in a router advertisement message being used by hosts instead of the standardized default value. If a very small value was configured and advertised to hosts on the LAN segment, communications would fail due to the hop limit reaching zero before the packets sent by a host reached its destination.

Check Content

Enter the "show ipv6 int" command on the leaf switch to verify the configuration was pushed out correctly to the leaf switch. interface Ethernet 1/1 ipv6 router advertisement hop-limit 32 If a hop limit of at least 32 is not advertised in Cisco ACI advertisement messages for IPv6 stateless auto-configuration deployments, this is a finding.

Fix Text

Configure the switch to advertise a hop limit of at least 32 in router advertisement messages as shown in the example. Depending on the ACI configuration, it may be necessary to specify the appropriate context (like a specific VLAN or L3Out) before issuing the command. apic1(config)# interface Ethernet 1/1 apic1(config-if)# ipv6 router advertisement hop-limit 32 Note: When configuring using a VPC interface, the ND RA prefix must be enabled for both side A and side B as both are members in the VPC configuration. Enable the ND RA prefix: 1. In the Work Pane, in the Logical Interface Profile screen, click the SVI tab. 2. Under Properties, click the check boxes to enable the ND RA Prefix for both Side A and Side B. Choose the identical ND RA Prefix Policy for Side A and Side B.

Additional Identifiers

Rule ID: SV-272100r1064609_rule

Vulnerability ID: V-272100

Group Title: SRG-NET-000512-RTR-000012

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.