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The Cisco Multicast Source Discovery Protocol (MSDP) router must be configured to only accept MSDP packets from known MSDP peers.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-96843 | CISC-RT-000900 | SV-105981r1_rule | Medium |
| Description |
|---|
| MSDP peering with customer network routers presents additional risks to the DISN Core, whether from a rogue or misconfigured MSDP-enabled router. To guard against an attack from malicious MSDP traffic, the receive path or interface filter for all MSDP-enabled RP routers must be configured to only accept MSDP packets from known MSDP peers. |
| STIG | Date |
|---|---|
| Cisco IOS XR Router RTR Security Technical Implementation Guide | 2019-07-24 |
Details
| Check Text ( C-95679r1_chk ) |
|---|
| Review the router configuration to determine if there is a receive path or interface filter to only accept MSDP packets from known MSDP peers. Step 1: Determine which interfaces would be peering MSDP with an external router by the configured peer addresses as shown in the example below. router msdp peer x.14.2.1 remote-as nn ! peer x.15.3.5 remote-as nn ! ! Step 2: Verify that interfaces used for MSDP peering have an inbound ACL as shown in the example. interface GigabitEthernet0/0/0/1 ipv4 address x.14.2.2 255.255.255.252 ipv4 access-group EXTERNAL_ACL_INBOUND ingress Step 3: Verify that the ACL restricts MSDP peering to only known sources. ipv4 access-list EXTERNAL_ACL_INBOUND 10 permit tcp host x.1.28.2 host x.1.28.8 eq 639 20 deny tcp any host x.1.28.8 eq 639 log 30 permit tcp host x.1.28.2 host x.1.28.8 eq bgp 40 permit tcp host x.1.28.2 eq bgp host x.1.28.8 50 permit pim host x.1.28.2 host x.1.28.8 60 permit tcp any any established … … … 140 deny ipv4 any any log Note: MSDP connections is via TCP port 639 If the router is not configured to only accept MSDP packets from known MSDP peers, this is a finding. |
| Fix Text (F-102523r1_fix) |
|---|
| Configure the interface ACLs to only accept MSDP packets from known MSDP peers. RP/0/0/CPU0:R2(config)#ipv4 access-list EXTERNAL_ACL_INBOUND RP/0/0/CPU0:R2(config-ipv4-acl)#permit tcp host x.1.28.2 host x.1.28.8 eq 639 RP/0/0/CPU0:R2(config-ipv4-acl)#deny tcp any host x.1.28.8 eq 639 log RP/0/0/CPU0:R2(config-ipv4-acl)#permit tcp host x.1.28.2 host x.1.28.8 eq bgp RP/0/0/CPU0:R2(config-ipv4-acl)#permit tcp host x.1.28.2 eq bgp host x.1.28.8 RP/0/0/CPU0:R2(config-ipv4-acl)#permit pim host x.1.28.2 host x.1.28.8 RP/0/0/CPU0:R2(config-ipv4-acl)#permit tcp any any established … … … RP/0/0/CPU0:R2(config-ipv4-acl)#deny ip any any log |