Title

The Cisco ACI multicast rendezvous point (RP) must be configured to limit the multicast forwarding cache so that its resources are not saturated by managing an overwhelming number of Protocol Independent Multicast (PIM) and Multicast Source Discovery Protocol (MSDP) source-active entries. (Cat III impact)

Discussion

MSDP peering between networks enables sharing of multicast source information. Enclaves with an existing multicast topology using PIM-SM can configure their RP routers to peer with MSDP routers. As a first step of defense against a denial-of-service (DoS) attack, all RP routers must limit the multicast forwarding cache to ensure that router resources are not saturated managing an overwhelming number of PIM and MSDP source-active entries.

Check Content

Review the PIM configuration: ip pim register-rate-limit 10 If the RP router is not configured to filter PIM register messages, rate limiting the number of PIM register messages, and accept MSDP packets only from known MSDP peers, this is a finding.

Fix Text

Configure the switch to filter PIM register messages, rate limiting the number of PIM register messages, and accept MSDP packets only from known MSDP peers. Use the command "ip pim register-rate-limit <rate>", where <rate> specifies the desired maximum number of register messages per second allowed to be sent. Navigate to the global configuration mode. [switch#] configure terminal [switch(config)#] ip pim register-rate-limit 10

Additional Identifiers

Rule ID: SV-272090r1064597_rule

Vulnerability ID: V-272090

Group Title: SRG-NET-000362-RTR-000120

Expert Comments

CCIs tied to check.

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