The Cisco switch must have the default VLAN pruned from all trunk ports that do not require it.
An XCCDF Rule
Description
<VulnDiscussion>The default VLAN (i.e., VLAN 1) is a special VLAN used for control plane traffic such as Spanning-Tree Protocol (STP), Dynamic Trunking Protocol (DTP), VLAN Trunking Protocol (VTP), and Port Aggregation Protocol (PAgP). VLAN 1 is enabled on all trunks and ports by default. With larger campus networks, care must be taken about the diameter of the STP domain for the default VLAN. Instability in one part of the network could affect the default VLAN, influencing control-plane stability and therefore STP stability for all other VLANs.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>
- ID
- SV-220643r991850_rule
- Severity
- Medium
- References
- Updated
Remediation - Manual Procedure
Prune VLAN 1 from any trunk links as necessary:
SW1(config)#int g0/2
SW1(config-if)#switchport trunk allowed vlan except 1
Verify that VLAN 1 is not allowed on the trunk link: