The Cisco perimeter router must be configured to drop IPv6 undetermined transport packets.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-230049	CISC-RT-000392	SV-230049r533189_rule		Medium

Description
One of the fragmentation weaknesses known in IPv6 is the undetermined transport packet. This packet contains an undetermined protocol due to fragmentation. Depending on the length of the IPv6 extension header chain, the initial fragment may not contain the layer four port information of the packet.

STIG	Date
Cisco IOS XR Router RTR Security Technical Implementation Guide	2020-09-23

Details

Check Text ( C-32356r533186_chk )

This requirement is not applicable for the DODIN Backbone. Review the router configuration to determine if it is configured to drop IPv6 undetermined transport packets. Step 1: Verify that an inbound IPv6 ACL has been configured on the external interface. interface interface gigabitethernet 0/2/0/2 ipv6 address 2001::1:0:22/64 ipv6 access-group FILTER_IPV6 ingress Step 2: Verify that the ACL drops undetermined transport packets as shown in the example below. ipv6 access-list FILTER_IPV6 10 deny ipv6 any any log undetermined-transport 20 permit ipv6 … … … … 90 deny ipv6 any any log If the router is not configured to drop IPv6 undetermined transport packets, this is a finding.

Fix Text (F-32334r533188_fix)

Configure the router to drop IPv6 undetermined transport packets as shown in the example below. RP/0/0/CPU0:R3(config)# ipv6 access-list FILTER_IPV6 RP/0/0/CPU0:R3(config-ipv6-acl)# deny ipv6 any any undetermined-transport log RP/0/0/CPU0:R3(config-ipv6-acl)# permit ipv6 … … … … RP/0/0/CPU0:R3(config-ipv6-acl)# deny ipv6 any any log RP/0/0/CPU0:R3(config-ipv6-acl)# exit RP/0/0/CPU0:R3(config)# interface gigabitethernet 0/2/0/2 RP/0/0/CPU0:R3(config-if)# ipv6 access-group FILTER_IPV6 ingress