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 a multicast group only from sources that have been approved by the organization.

DISA Rule

SV-216815r531087_rule

Vulnerability Number

V-216815

Group Title

SRG-NET-000364-RTR-000115

Rule Version

CISC-RT-000870

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 DR to filter the IGMP and MLD report messages to allow hosts to join only those multicast groups from sources that have been approved as shown in the example.

Step 1: Configure the access list to filter multicast joins as shown in the example below.

RP/0/0/CPU0:R2(config)#ipv4 access-list IGMP_JOIN_FILTER
RP/0/0/CPU0:R2(config-ipv4-acl)#deny ip any 232.8.0.0 0.0.255.255
RP/0/0/CPU0:R2(config-ipv4-acl)#permit ip x.0.0.0 0.255.255.255 any
RP/0/0/CPU0:R2(config-ipv4-acl)#deny ip any any

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 report messages, allowing hosts to only join multicast groups from sources 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 sources or allows only authorized sources. The example below denies all groups from 232.8.0.0/16 range and permits sources only from the x.0.0.0/8 network.

ipv4 access-list IGMP_JOIN_FILTER
10 deny ipv4 any 232.8.0.0 0.0.255.255
20 permit ipv4 x.0.0.0 0.255.255.255 any
30 deny ipv4 any any
!

Note: This requirement is only applicable to Source Specific Multicast (SSM) implementation.

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

Vulnerability Number

V-216815

Documentable

False

Rule Version

CISC-RT-000870

Severity Override Guidance

Review the configuration of the DR to verify that it is filtering IGMP or MLD report messages, allowing hosts to only join multicast groups from sources 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 sources or allows only authorized sources. The example below denies all groups from 232.8.0.0/16 range and permits sources only from the x.0.0.0/8 network.

ipv4 access-list IGMP_JOIN_FILTER
10 deny ipv4 any 232.8.0.0 0.0.255.255
20 permit ipv4 x.0.0.0 0.255.255.255 any
30 deny ipv4 any any
!

Note: This requirement is only applicable to Source Specific Multicast (SSM) implementation.

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

Check Content Reference

M

Target Key

4029

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