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The Cisco Multicast Source Discovery Protocol (MSDP) switch must be configured to only accept MSDP packets from known MSDP peers.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-221064 | CISC-RT-000900 | SV-221064r622190_rule | Medium |
| Description |
|---|
| MSDP peering with customer network switches presents additional risks to the DISN Core, whether from a rogue or misconfigured MSDP-enabled switch. To guard against an attack from malicious MSDP traffic, the receive path or interface filter for all MSDP-enabled RP switches must be configured to only accept MSDP packets from known MSDP peers. |
| STIG | Date |
|---|---|
| Cisco IOS-XE Switch RTR Security Technical Implementation Guide | 2021-03-26 |
Details
| Check Text ( C-22779r408986_chk ) |
|---|
| Review the switch configuration to determine if there is a receive path or interface filter to only accept MSDP packets from known MSDP peers. Step 1: Verify that interfaces used for MSDP peering have an inbound ACL as shown in the example below: interface GigabitEthernet1/1 no switchport ip address x.1.28.8 255.255.255.0 ip access-group EXTERNAL_ACL_INBOUND in ip pim sparse-mode Step 2: Verify that the ACL restricts MSDP peering to only known sources. ip access-list extended EXTERNAL_ACL_INBOUND permit tcp any any established permit tcp host x.1.28.2 host x.1.28.8 eq 639 deny tcp any host x.1.28.8 eq 639 log permit tcp host x.1.28.2 host 10.1.28.8 eq bgp permit tcp host x.1.28.2 eq bgp host x.1.28.8 permit pim host x.1.28.2 host x.1.28.8 … … … deny ip any any log Note: MSDP connections is via TCP port 639. If the switch is not configured to only accept MSDP packets from known MSDP peers, this is a finding. |
| Fix Text (F-22768r408987_fix) |
|---|
| Configure the receive path or interface ACLs to only accept MSDP packets from known MSDP peers. SW1(config)#ip access-list extended EXTERNAL_ACL_INBOUND SW1(config-ext-nacl)#permit tcp any any established SW1(config-ext-nacl)#permit tcp host x.1.28.2 host x.1.28.8 eq 639 SW1(config-ext-nacl)#deny tcp any host x1.28.8 eq 639 SW1(config-ext-nacl)#permit tcp host x.1.28.2 host x.1.28.8 eq bgp SW1(config-ext-nacl)#permit tcp host x.1.28.2 eq bgp host x.1.28.8 SW1(config-ext-nacl)#permit pim host x.1.28.2 host x.1.28.8 … … … SW1(config-ext-nacl)#deny ip any any |