JUEX-L2-000110 - The Juniper EX switch must be configured not to forward unknown unicast traffic to access interfaces.

Information

Access layer switches use the Content Addressable Memory (CAM) table to direct traffic to specific interfaces based on the VLAN number and the destination MAC address of the frame. When a router has an Address Resolution Protocol (ARP) entry for a destination host and forwards it to the access layer switch and there is no entry corresponding to the frame's destination MAC address in the incoming VLAN, the frame will be sent to all forwarding interfaces within the respective VLAN, which causes flooding. Large amounts of flooded traffic can saturate low-bandwidth links, causing network performance issues or complete connectivity outage to the connected devices. Unknown unicast flooding has been a nagging problem in networks that have asymmetric routing and default timers. To mitigate the risk of a connectivity outage, the unknown unicast traffic must not be flooded to all access interfaces.

NOTE: Nessus has provided the target output to assist in reviewing the benchmark to ensure target compliance.

Solution

Configure the switch to have VLANs forward unknown unicast frames to a single interface.

set switch-options unknown-unicast-forwarding vlan <VLAN name> interface <interface name>.<logical unit>

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Juniper_EX_Switches_Y24M07_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-5, CAT|II, CCI|CCI-002385, Rule-ID|SV-253958r843907_rule, STIG-ID|JUEX-L2-000110, Vuln-ID|V-253958

Plugin: Juniper

Control ID: 219a4c5764d6af6a316499eaf0a562647b08ec58ab6452520e11889e32a00c29