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


Overview

Finding ID Version Rule ID IA Controls Severity
V-237774 CISC-RT-000396 SV-237774r856671_rule Medium
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.
STIG Date
Cisco IOS XE Switch RTR Security Technical Implementation Guide 2024-06-06

Details

Check Text ( C-40986r856265_chk )
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 an extension header with the Endpoint Identification option as shown in the example below.

ipv6 access-list FILTER_IPV6
deny any any dest-option-type 138 log
permit ipv6 …



deny ipv6 any any log


If the switch is not configured to drop IPv6 packets containing an extension header with the Endpoint Identification option, this is a finding.
Fix Text (F-40945r856266_fix)
Configure the switch to drop IPv6 packets containing an option type values 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 any any dest-option-type 138 log
SW1(config-ipv6-acl)#permit ipv6 …



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