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The Cisco multicast edge switch must be configured to establish boundaries for administratively scoped multicast traffic.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-101983 | CISC-RT-000810 | SV-111087r1_rule | Low |
| Description |
|---|
| If multicast traffic is forwarded beyond the intended boundary, it is possible that it can be intercepted by unauthorized or unintended personnel. Administrative scoped multicast addresses are locally assigned and are to be used exclusively by the enterprise network or enclave. Administrative scoped multicast traffic must not cross the enclave perimeter in either direction. Restricting multicast traffic makes it more difficult for a malicious user to access sensitive traffic. Admin-Local scope is encouraged for any multicast traffic within a network intended for network management, as well as for control plane traffic that must reach beyond link-local destinations. |
| STIG | Date |
|---|---|
| Cisco NX-OS Switch RTR Security Technical Implementation Guide | 2020-05-20 |
Details
| Check Text ( C-100871r1_chk ) |
|---|
| Multicast boundary for NX-OS can be established via combination of the border command along with an ACL to filter admin-scoped multicast traffic. Step 1: Verify that the interface at the multicast domain edge has been configured with both an ingress and egress ACL. interface Ethernet2/1 no switchport ip access-group FILTER_TRAFFIC_IN in ip access-group FILTER_TRAFFIC_OUT out ip address 10.1.12.1/24 ip pim sparse-mode ip pim border Note: The command ip pim border enables the interface to be on the border of PIM domain so that no bootstrap, candidate-RP, or Auto-RP messages are sent or received on the interface. Step 2: Verify that the ingress and egress ACLs block the address range for administratively scoped multicast traffic. ip access-list FILTER_TRAFFIC_IN 10 deny ip any 239.0.0.0/8 20 permit tcp any any established … … … 90 deny ip any any log ip access-list FILTER_TRAFFIC_OUT 10 deny ip any 239.0.0.0/8 20 deny ip … … 80 permit ip any any If the switch is not configured to establish boundaries for administratively scoped multicast traffic, this is a finding. |
| Fix Text (F-107665r1_fix) |
|---|
| Step 1: Configure an ingress and egress ACL to block administratively scoped multicast traffic. SW1(config)# ip access-list FILTER_TRAFFIC_IN SW1(config-acl)# deny 239.0.0.0/8 SW1(config-acl)# permit tcp any any established SW1(config-acl)# … SW1(config-acl)# deny ip any any log SW1(config-acl)# exit SW1(config)# ip access-list FILTER_TRAFFIC_OUT SW1(config-acl)# deny 239.0.0.0/8 SW1(config-acl)# … SW1(config-acl)# permit ip any any SW1(config-acl)# exit Step 2: Apply the ingress and egress ACL to the applicable interfaces. SW1(config)# int e2/1 SW1(config-if)# ip access-group FILTER_TRAFFIC_IN in SW1(config-if)# ip access-group FILTER_TRAFFIC_OUT out SW1(config-if)# end |