The Cisco multicast Rendezvous Point (RP) router must be configured to filter Protocol Independent Multicast (PIM) Join messages received from the Designated Router (DR) for any undesirable multicast groups.
An XCCDF Rule
Description
<VulnDiscussion>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.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>
- ID
- SV-216810r856449_rule
- Severity
- Low
- References
- Updated
Remediation - Manual Procedure
The risk associated with this requirement can be fully mitigated by configuring the router to filter PIM register messages, rate limiting the number of PIM register messages, and accept MSDP packets only from known MSDP peers.
Step 1: Configure the router to filter PIM register messages received from a multicast DR for any undesirable multicast groups and sources. The example below will deny any multicast streams for groups 239.5.0.0/16 and allow from only sources 10.1.2.6 and 10.1.2.7.
RP/0/0/CPU0:R2(config)#ipv4 access-list PIM_REGISTER_FILTER
RP/0/0/CPU0:R2(config-ipv4-acl)#deny ipv4 any 239.5.0.0 0.0.255.255