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

From Perimeter Router Security Technical Implementation Guide Juniper

Part of Maximum hop limit is less than 32

SV-40390r1_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.

Check content

Review the router or multi-layer switch configuration to determine if the default maximum hop limit has been configured. If it has been configured, then it must be set to at least 32. protocols { … … router-advertisement { interface [fe-1/1/1 fe-1/1/2] { current-hop-limit 128; } … } } Note: The JUNOS 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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