The Arista 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.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-256046	ARST-RT-000670	SV-256046r882480_rule		Medium

Description
Real-time multicast traffic can entail multiple large flows of data. Large unicast flows tend to be fairly isolated (i.e., someone doing a file download here or there), whereas multicast can have broader impact on bandwidth consumption, resulting in extreme network congestion. Hence, it is imperative that there is multicast admission control to restrict which multicast groups hosts are allowed to join via IGMP or MLD.

Description

Real-time multicast traffic can entail multiple large flows of data. Large unicast flows tend to be fairly isolated (i.e., someone doing a file download here or there), whereas multicast can have broader impact on bandwidth consumption, resulting in extreme network congestion. Hence, it is imperative that there is multicast admission control to restrict which multicast groups hosts are allowed to join via IGMP or MLD.

STIG	Date
Arista MLS EOS 4.2x Router Security Technical Implementation Guide	2023-01-17

Details

Check Text ( C-59722r882478_chk )
Review the configuration of the Arista DR to verify it is filtering IGMP or MLD report messages, allowing hosts to only join multicast groups from sources that have been approved. Note: This requirement is only applicable to Source Specific Multicast (SSM) implementation. Step 1: To verify the ACL filters the unauthorized IGMP joins, execute the command "sh ip access-list". ip access-list standard ALLOWED_SOURCES 10 permit 232.0.0.0/8 20 deny any log Step 2: Verify the ACL is configured on internal host-facing interfaces (pim process) to filter IGMP joins. router pim sparse-mode ipv4 ssm range ALLOWED_SOURCES If the Arista DR is not filtering IGMP or MLD report messages, this is a finding.

Check Text ( C-59722r882478_chk )

Review the configuration of the Arista DR to verify it is filtering IGMP or MLD report messages, allowing hosts to only join multicast groups from sources that have been approved.

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

Step 1: To verify the ACL filters the unauthorized IGMP joins, execute the command "sh ip access-list".

ip access-list standard ALLOWED_SOURCES
10 permit 232.0.0.0/8
20 deny any log

Step 2: Verify the ACL is configured on internal host-facing interfaces (pim process) to filter IGMP joins.

router pim sparse-mode
ipv4
ssm range ALLOWED_SOURCES

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

Fix Text (F-59665r882479_fix)
Configure the Arista DR to filter the IGMP and MLD report messages to allow hosts to join only multicast groups from sources that have been approved. Step 1: Configure the ACL to filter the unauthorized IGMP groups. LEAF-1A(config-if-Et3)#ip access-list standard ALLOWED_SOURCES LEAF-1A(config-std-acl-ALLOWED_SOURCES)# 10 permit 232.0.0.0/8 LEAF-1A(config-std-acl-ALLOWED_SOURCES)# 20 deny any log Step 2: Configure the IGMP filter in IGMP process. LEAF-1A(config)#router pim sparse-mode LEAF-1A(config-router-pim-sparse)# ipv4 LEAF-1A(config-router-pim-sparse-ipv4)# ssm range ALLOWED_SOURCES

Fix Text (F-59665r882479_fix)

Configure the Arista DR to filter the IGMP and MLD report messages to allow hosts to join only multicast groups from sources that have been approved.

Step 1: Configure the ACL to filter the unauthorized IGMP groups.

LEAF-1A(config-if-Et3)#ip access-list standard ALLOWED_SOURCES
LEAF-1A(config-std-acl-ALLOWED_SOURCES)# 10 permit 232.0.0.0/8
LEAF-1A(config-std-acl-ALLOWED_SOURCES)# 20 deny any log

Step 2: Configure the IGMP filter in IGMP process.

LEAF-1A(config)#router pim sparse-mode
LEAF-1A(config-router-pim-sparse)# ipv4
LEAF-1A(config-router-pim-sparse-ipv4)# ssm range ALLOWED_SOURCES