STIGQter: STIG Summary: Cisco IOS 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-216629r531085_rule

Vulnerability Number

V-216629

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.

R3(config)#ip access-list standard IGMP_JOIN_FILTER
R3(config-std-nacl)#deny 239.8.0.0 0.0.255.255
R3(config-std-nacl)#permit any
R3(config-std-nacl)#exit

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

R3(config)#int g0/0
R3(config-if)#ip igmp access-group IGMP_JOIN_FILTER

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.

interface GigabitEthernet0/0
ip address 10.3.3.3 255.255.255.0
ip pim sparse-mode
ip igmp access-group IGMP_JOIN_FILTER
ip igmp version 3

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

ip access-list standard IGMP_JOIN_FILTER
deny 239.8.0.0 0.0.255.255
permit 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-216629

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.

interface GigabitEthernet0/0
ip address 10.3.3.3 255.255.255.0
ip pim sparse-mode
ip igmp access-group IGMP_JOIN_FILTER
ip igmp version 3

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

ip access-list standard IGMP_JOIN_FILTER
deny 239.8.0.0 0.0.255.255
permit 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

4027

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