V-217087

Discussion

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 and sources.

Check Content

Review the RP router configuration to determine if it filters PIM join messages for any reserved multicast groups.

Step 1: Verify that a PIM import statement has been configured as shown in the example below:

protocols {
    …
    …
    …
    }
    pim {
           import MULTICAST_JOIN_POLICY;

Step 2: Verify that the join policy has defined both bad multicast groups and sources as shown in the example below:

policy-options {
    …
    …
    …
    }
    policy-statement MULTICAST_JOIN_POLICY {
        term BAD_GROUPS {
            from {
                route-filter 224.1.1.0/24 orlonger;
                route-filter 225.1.2.3/32 exact;
                …
                …
                …
                route-filter 232.0.0.0/8 orlonger;
            }
            then reject;
        }
        term ALLOW_OTHER {
            then accept;
        }
    }
If the RP router peering with PIM-SM routers is not configured with a PIM import policy to block join messages for any undesirable multicast groups, this is a finding.