STIGQter: STIG Summary: Cisco IOS XE Router RTR Security Technical Implementation Guide Version: 2 Release: 2 Benchmark Date: 23 Apr 2021:

The Cisco Multicast Source Discovery Protocol (MSDP) router must be configured to only accept MSDP packets from known MSDP peers.

DISA Rule

SV-216728r531086_rule

Vulnerability Number

V-216728

Group Title

SRG-NET-000364-RTR-000116

Rule Version

CISC-RT-000900

Severity

CAT II

CCI(s)

• CCI-002403 - The information system only allows incoming communications from organization-defined authorized sources routed to organization-defined authorized destinations.

Weight

10

Fix Recommendation

Configure the receive path or interface ACLs to only accept MSDP packets from known MSDP peers.

R8(config)#ip access-list extended EXTERNAL_ACL_INBOUND
R8(config-ext-nacl)#permit tcp any any established
R8(config-ext-nacl)#permit tcp host x.1.28.2 host x.1.28.8 eq 639
R8(config-ext-nacl)#deny tcp any host x1.28.8 eq 639
R8(config-ext-nacl)#permit tcp host x.1.28.2 host x.1.28.8 eq bgp
R8(config-ext-nacl)#permit tcp host x.1.28.2 eq bgp host x.1.28.8
R8(config-ext-nacl)#permit pim host x.1.28.2 host x.1.28.8
…
…
…
R8(config-ext-nacl)#deny ip any any

Check Contents

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: Verify that interfaces used for MSDP peering have an inbound ACL as shown in the example.

interface GigabitEthernet1/1
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 pim host x.1.28.8
…
…
…
deny ip 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.

Vulnerability Number

V-216728

Documentable

False

Rule Version

CISC-RT-000900

Severity Override Guidance

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: Verify that interfaces used for MSDP peering have an inbound ACL as shown in the example.

interface GigabitEthernet1/1
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 pim host x.1.28.8
…
…
…
deny ip 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.

Check Content Reference

M

Target Key

4028

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