The Cisco switch must be configured to advertise a hop limit of at least 32 in Switch Advertisement messages for IPv6 stateless auto-configuration deployments.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-237754	CISC-RT-000236	SV-237754r648783_rule		Low

Description
The Neighbor Discovery protocol allows a hop limit value to be advertised by routers in a Router Advertisement message being used by hosts instead of the standardized default value. If a very small value was configured and advertised to hosts on the LAN segment, communications would fail due to the hop limit reaching zero before the packets sent by a host reached its destination.

STIG	Date
Cisco NX-OS Switch RTR Security Technical Implementation Guide	2021-03-29

Details

Check Text ( C-40972r648781_chk )
Review the switch configuration to determine if the hop limit has been configured for Router Advertisement messages for all internal interfaces as shown in the example. interface Ethernet2/1 no switchport ipv6 address 2001::1:0:1/64 ipv6 nd hop-limit 32 no shutdown interface Ethernet2/2 no switchport ipv6 address 2001::1:1:1/64 ipv6 nd hop-limit 32 no shutdown If hop-limit has been configured and has not been set to at least 32, it is a finding.

Check Text ( C-40972r648781_chk )

Review the switch configuration to determine if the hop limit has been configured for Router Advertisement messages for all internal interfaces as shown in the example.

interface Ethernet2/1
no switchport
ipv6 address 2001::1:0:1/64
ipv6 nd hop-limit 32
no shutdown

interface Ethernet2/2
no switchport
ipv6 address 2001::1:1:1/64
ipv6 nd hop-limit 32
no shutdown

If hop-limit has been configured and has not been set to at least 32, it is a finding.

Fix Text (F-40934r648782_fix)
Configure the switch to advertise a hop limit of at least 32 in Router Advertisement messages as shown in the example. SW1(config)# interface e2/1 – 2 SW1(config-if-range)# ipv6 nd hop-limit 32 SW1(config-if-range)# end