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V-237754

CAT III (Low)

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.

Rule ID

SV-237754r999759_rule

STIG

Cisco NX OS Switch RTR Security Technical Implementation Guide

Version

V3R4

CCIs

CCI-000366

Discussion

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.

Check Content

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

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