STIGQter: STIG Summary: Cisco IOS XR Router RTR Security Technical Implementation Guide Version: 2 Release: 1 Benchmark Date: 23 Oct 2020:

The Cisco multicast Designated Router (DR) must be configured to filter the Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Report messages to allow hosts to join only multicast groups that have been approved by the organization.

DISA Rule

SV-216814r531087_rule

Vulnerability Number

V-216814

Group Title

SRG-NET-000364-RTR-000114

Rule Version

CISC-RT-000860

Severity

CAT III

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 DR to filter the IGMP or MLD Membership Report messages to allow hosts to join only those multicast groups that have been approved.

Step 1: Configure the ACL to filter IGMP Membership Report messages as shown in the example.

RP/0/0/CPU0:R5(config)#ipv4 access-list IGMP_JOIN_FILTER
RP/0/0/CPU0:R5(config-ipv4-acl)#deny 239.8.0.0 0.0.255.255
RP/0/0/CPU0:R5(config-ipv4-acl)#exit

Step 2: Apply the filter to all host facing interfaces.

RP/0/0/CPU0:R5(config)#router igmp
RP/0/0/CPU0:R5(config-igmp)#interface g0/0/1/0
RP/0/0/CPU0:R5(config-igmp-default-if)#access-group IGMP_JOIN_FILTER
RP/0/0/CPU0:R5(config-igmp-default-if)#exit
RP/0/0/CPU0:R5(config-igmp)#interface g0/0/1/1
RP/0/0/CPU0:R5(config-igmp-default-if)#end

Check Contents

Review the configuration of the DR to verify that it is filtering IGMP or MLD Membership Report messages, allowing hosts to join only those groups that have been approved.

Step 1: Verify that all host facing interfaces are configured to filter IGMP Membership Report messages (IGMP joins) as shown in the example below.

router igmp
interface GigabitEthernet0/0/1/0
access-group IGMP_JOIN_FILTER
!
interface GigabitEthernet0/0/1/1
access-group IGMP_JOIN_FILTER
!

Step 2: Verify that the ACL denies unauthorized groups or permits only authorized groups. The example below denies all groups from 239.8.0.0/16 range.

ipv4 access-list IGMP_JOIN_FILTER
10 deny ipv4 239.8.0.0 0.0.255.255 any
20 permit ipv4 any any
!

Note: This requirement is only applicable to Source Specific Multicast (SSM) implementation. This requirement is not applicable to Any Source Multicast (ASM) since the filtering is being performed by the Rendezvous Point router.

If the DR is not filtering IGMP or MLD Membership Report messages, this is a finding.

Vulnerability Number

V-216814

Documentable

False

Rule Version

CISC-RT-000860

Severity Override Guidance

Review the configuration of the DR to verify that it is filtering IGMP or MLD Membership Report messages, allowing hosts to join only those groups that have been approved.

Step 1: Verify that all host facing interfaces are configured to filter IGMP Membership Report messages (IGMP joins) as shown in the example below.

router igmp
interface GigabitEthernet0/0/1/0
access-group IGMP_JOIN_FILTER
!
interface GigabitEthernet0/0/1/1
access-group IGMP_JOIN_FILTER
!

Step 2: Verify that the ACL denies unauthorized groups or permits only authorized groups. The example below denies all groups from 239.8.0.0/16 range.

ipv4 access-list IGMP_JOIN_FILTER
10 deny ipv4 239.8.0.0 0.0.255.255 any
20 permit ipv4 any any
!

Note: This requirement is only applicable to Source Specific Multicast (SSM) implementation. This requirement is not applicable to Any Source Multicast (ASM) since the filtering is being performed by the Rendezvous Point router.

If the DR is not filtering IGMP or MLD Membership Report messages, this is a finding.

Check Content Reference

M

Target Key

4029

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