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.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-216812 | CISC-RT-000840 | SV-216812r531087_rule | Low |
| Description |
|---|
| Real-time multicast traffic can entail multiple large flows of data. An attacker can flood a network segment with multicast packets, over-using the available bandwidth and thereby creating a denial-of-service (DoS) condition. Hence, it is imperative that join messages are only accepted for authorized multicast groups. |
| STIG | Date |
|---|---|
| Cisco IOS XR Router RTR Security Technical Implementation Guide | 2020-09-23 |
Details
| Check Text ( C-18044r288810_chk ) |
|---|
| Verify that the RP router is configured to filter PIM join messages for any undesirable multicast groups. In the example below, groups from 239.8.0.0/16 are no allowed. ipv4 access-list FILTER_PIM_JOINS 10 deny ipv4 239.8.0.0 0.0.255.255 any 20 permit ipv4 any any … … … router pim address-family ipv4 allow-rp group-list FILTER_PIM_JOINS If the RP is not configured to filter join messages received from the DR for any undesirable multicast groups, this is a finding. |
| Fix Text (F-18042r288811_fix) |
|---|
| Configure the RP to filter PIM join messages for any undesirable multicast groups as shown in the example below. RP/0/0/CPU0:R2(config)#ipv4 access-list FILTER_PIM_JOINS RP/0/0/CPU0:R2(config-ipv4-acl)#deny 239.8.0.0 0.0.255.255 RP/0/0/CPU0:R2(config-ipv4-acl)#permit any RP/0/0/CPU0:R2(config-ipv4-acl)#exit RP/0/0/CPU0:R2(config)#router pim RP/0/0/CPU0:R2(config-pim)#address-family ipv4 RP/0/0/CPU0:R2(config-pim-default-ipv4)#allow-rp group-list FILTER_PIM_JOINS RP/0/0/CPU0:R2(config-pim-default-ipv4)#end |