The administrator must ensure that the maximum hop limit is at least 32.

From Infrastructure Router Security Technical Implementation Guide Cisco

Part of Maximum hop limit is less than 32

SV-40389r1_rule The administrator must ensure that the maximum hop limit is at least 32.

Vulnerability discussion

The Neighbor Discovery protocol allows a hop limit value to be advertised by routers in a Router Advertisement message to be 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 hop limit reaching zero before the packets sent by a host reached its destination.

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The maximum number of hops used in router advertisements and all IPv6 packets that are originated by the router can be set using the ipv6 hop-limit command in global configuration mode. Review the router or multi-layer switch configuration to determine if the maximum hop limit has been configured. If it has been configured, then it must be set to at least 32. The following global command sets the max hop limit to 128: ipv6 hop-limit 128 Note: The IOS default is 64. Hence, if the hop limit is not configured, the router will be in compliance with the requirement.

Fix text

Configure maximum hop limit to at least 32.

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