The Cisco perimeter switch must be configured to drop IPv6 packets containing an extension header with the Endpoint Identification option.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-237773	SRG-NET-000364-RTR-000204	CISC-RT-000396	SV-237773r1135078_rule	2025-08-22	3

Description
The optional and extensible natures of the IPv6 extension headers require higher scrutiny since many implementations do not always drop packets with headers that it cannot recognize, and hence could cause a Denial-of-Service on the target device. In addition, the type, length, value (TLV) formatting provides the ability for headers to be very large. This option type is associated with the Nimrod Routing system and has no defining RFC document.

Description

The optional and extensible natures of the IPv6 extension headers require higher scrutiny since many implementations do not always drop packets with headers that it cannot recognize, and hence could cause a Denial-of-Service on the target device. In addition, the type, length, value (TLV) formatting provides the ability for headers to be very large. This option type is associated with the Nimrod Routing system and has no defining RFC document.

ℹ️ Check
This requirement is not applicable for the DODIN Backbone. Review the switch configuration to determine if it is compliant with this requirement. Step 1: Verify that an inbound IPv6 ACL has been configured on the external interface. interface gigabitethernet1/0 ipv6 address 2001::1:0:22/64 ipv6 traffic-filter FILTER_IPV6 in Step 2: Verify that the ACL drops IPv6 packets containing a Destination Option header as shown in the example below. ipv6 access-list FILTER_IPV6 deny 60 any any dest-option log permit ipv6 … … … … deny ipv6 any any log Note: Cisco has deprecated the dest-option-type command used to filter by option type within the Destination Option header. Therefore, all packets with the Destination Option header must be dropped. If the switch is not configured to drop IPv6 packets containing a Destination Option header, this is a finding.

ℹ️ Check

This requirement is not applicable for the DODIN Backbone. Review the switch configuration to determine if it is compliant with this requirement. Step 1: Verify that an inbound IPv6 ACL has been configured on the external interface. interface gigabitethernet1/0 ipv6 address 2001::1:0:22/64 ipv6 traffic-filter FILTER_IPV6 in Step 2: Verify that the ACL drops IPv6 packets containing a Destination Option header as shown in the example below. ipv6 access-list FILTER_IPV6 deny 60 any any dest-option log permit ipv6 … … … … deny ipv6 any any log Note: Cisco has deprecated the dest-option-type command used to filter by option type within the Destination Option header. Therefore, all packets with the Destination Option header must be dropped. If the switch is not configured to drop IPv6 packets containing a Destination Option header, this is a finding.

✔️ Fix
Configure the switch to drop IPv6 packets containing an option type value of 0x8A (Endpoint Identification) regardless of whether it appears in a Hop-by-Hop or Destination Option header as shown in the example below. SW1(config)#ipv6 access-list FILTER_IPV6 SW1(config-ipv6-acl)#deny 60 any any dest-option log SW1(config-ipv6-acl)#permit … … … … SW1(config-ipv6-acl)#deny ipv6 any any log SW1(config-ipv6-acl)#exit SW1(config)#int g1/0 SW1(config-if)#ipv6 traffic-filter FILTER_IPV6 SW1(config-if)#end

✔️ Fix

Configure the switch to drop IPv6 packets containing an option type value of 0x8A (Endpoint Identification) regardless of whether it appears in a Hop-by-Hop or Destination Option header as shown in the example below. SW1(config)#ipv6 access-list FILTER_IPV6 SW1(config-ipv6-acl)#deny 60 any any dest-option log SW1(config-ipv6-acl)#permit … … … … SW1(config-ipv6-acl)#deny ipv6 any any log SW1(config-ipv6-acl)#exit SW1(config)#int g1/0 SW1(config-if)#ipv6 traffic-filter FILTER_IPV6 SW1(config-if)#end