Rule ID
SV-220668r991905_rule
Version
V3R2
CCIs
CCI-004891
In a VLAN-based network, switches use the default VLAN (i.e., VLAN 1) for in-band management and to communicate with other networking devices using Spanning-Tree Protocol (STP), Dynamic Trunking Protocol (DTP), VLAN Trunking Protocol (VTP), and Port Aggregation Protocol (PAgP)—all untagged traffic. As a consequence, the default VLAN may unwisely span the entire network if not appropriately pruned. If its scope is large enough, the risk of compromise can increase significantly.
Review the switch configurations and verify that no access switch ports have been assigned membership to the default VLAN (i.e., VLAN 1). VLAN assignments can be verified via the show vlan command. SW1#show vlan VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active 10 User VLAN active Gi0/3, Gi1/0, Gi1/1, Gi1/2 Gi1/3, Gi2/1 20 Management VLAN active Gi0/2 999 VLAN0999 active Gi2/0 If there are access switch ports assigned to the default VLAN, this is a finding.
Remove the assignment of the default VLAN from all access switch ports.