STIGQter: STIG Summary: Cisco IOS Switch RTR Security Technical Implementation Guide Version: 2 Release: 1 Benchmark Date: 23 Apr 2021:

The Cisco multicast Designated switch (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-220464r622190_rule

Vulnerability Number

V-220464

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 multicast groups that have been approved.

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

SW2(config)#ip access-list standard IGMP_JOIN_FILTER
SW2(config-std-nacl)#deny 239.8.0.0 0.0.255.255
SW2(config-std-nacl)#permit any
SW2(config-std-nacl)#exit

Step 2: Apply the filter to all host-facing Layer 3 and VLAN interfaces.

SW2(config)#int vlan3
SW2(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 groups that have been approved.

Step 1: Verify that all host-facing Layer 3 and VLAN interfaces are configured to filter IGMP Membership Report messages (IGMP joins) as shown in the example below:

interface Vlan3
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 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 switch.

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

Vulnerability Number

V-220464

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 groups that have been approved.

Step 1: Verify that all host-facing Layer 3 and VLAN interfaces are configured to filter IGMP Membership Report messages (IGMP joins) as shown in the example below:

interface Vlan3
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 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 switch.

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

Check Content Reference

M

Target Key

4065

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