The Cisco multicast Rendezvous Point (RP) switch must be configured to filter Protocol Independent Multicast (PIM) Register messages received from the Designated switch (DR) for any undesirable multicast groups and sources.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-221057	CISC-RT-000830	SV-221057r622190_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 register messages are accepted only for authorized multicast groups and sources.

STIG	Date
Cisco IOS-XE Switch RTR Security Technical Implementation Guide	2022-09-13

Details

Check Text ( C-22772r408965_chk )

Verify that the RP is configured to filter PIM register messages. The example below will deny any multicast streams for groups 239.5.0.0/16 and allow from only sources x.1.2.6 and x.1.2.7. ip pim rp-address 10.1.12.3 ip pim accept-register list PIM_REGISTER_FILTER … … … ip access-list extended PIM_REGISTER_FILTER deny ip any 239.5.0.0 0.0.255.255 permit ip host x.1.2.6 any permit ip host x.1.2.7 any deny ip any any If the RP switch peering with PIM-SM switches is not configured with a policy to block registration messages for any undesirable multicast groups and sources, this is a finding.

Fix Text (F-22761r408966_fix)

Configure the switch 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 x.1.2.6 and x.1.2.7. SW2(config)#ip access-list extended PIM_REGISTER_FILTER SW2(config-ext-nacl)#deny ip any 239.5.0.0 0.0.255.255 SW2(config-ext-nacl)#permit ip host x.1.2.6 any SW2(config-ext-nacl)#permit ip host x.1.2.7 any SW2(config-ext-nacl)#deny ip any any SW2(config-ext-nacl)#exit SW2(config)#ip pim accept-register list PIM_REGISTER_FILTER SW2(config)#end