V-217086

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 register messages are accepted only for authorized multicast groups and sources.

Check Content

Verify that the RP router is configured to filter PIM register messages.

Verify that the RP has a register policy enabled as shown in the example below.

protocols {
    …
    …
    …
    }
    pim {
        rp {
            rp-register-policy MULTICAST_REGISTER_POLICY;
            local {
                address 2.2.2.2;
            }
        }

Verify that the register policy has defined both bad multicast groups and sources as shown in the example below.

policy-options {
    …
    …
    …
    }
    policy-statement MULTICAST_REGISTER_POLICY {
        term BAD_SOURCES {
            from {
                source-address-filter x.x.x.x/32 exact;
                source-address-filter x.x.x.x/24 orlonger;
            }
            then reject;
        }
        term BAD_GROUPS {
            from {
                route-filter 224.1.1.0/24 orlonger;
                route-filter 225.1.2.3/32 exact;
                route-filter 239.0.0.0/8 orlonger;
                …
                …
                …
                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 policy to block registration messages for any undesirable multicast groups and sources, this is a finding.