Information
The IAO/NSO will ensure VLAN1 is pruned from all trunk and access ports that do not require it.
VLAN 1 is a special VLAN that tags and handles most of the control plane traffic such as Spanning-Tree Protocol (STP), Cisco Discovery Protocol (CDP), Dynamic Trunking Protocol (DTP), VLAN Trunking Protocol (VTP), and Port Aggregation Protocol (PAgP)all VLAN 1 tagged traffic. VLAN 1 is enabled on all trunks and ports by default. With larger campus networks, care needs to be taken about the diameter of the VLAN 1 STP domain; instability in one part of the network could affect VLAN 1, thereby influencing control-plane stability and therefore STP stability for all other VLANs.
NOTE: This check is derived from the L3 switch guidance, if the scan target is a router the check can be ignored.
NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.
Solution
Best practice for VLAN-based networks is to prune unnecessary ports from gaining access to VLAN1 and insure that it does not traverse trunks not requiring VLAN1 traffic.