The layer 2 switch must not have the default VLAN assigned to any host-facing switch ports.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-206667	SRG-NET-000512-L2S-000008	SV-206667r385561_rule		Medium

Description
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.

Description

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.

STIG	Date
Layer 2 Switch Security Requirements Guide	2024-05-30

Details

Check Text ( C-6925r298431_chk )
Review the switch configurations and verify that no access switch ports have been assigned membership to the default VLAN (i.e., VLAN 1). A good method of ensuring there is not membership to the default VLAN is to have it disabled (i.e., shutdown) on the switch. This technique does not prevent switch control plane protocols such as CDP, DTP, VTP, and PAgP from using the default VLAN. If there are access switch ports assigned to the default VLAN, this is a finding.

Check Text ( C-6925r298431_chk )

Review the switch configurations and verify that no access switch ports have been assigned membership to the default VLAN (i.e., VLAN 1). A good method of ensuring there is not membership to the default VLAN is to have it disabled (i.e., shutdown) on the switch. This technique does not prevent switch control plane protocols such as CDP, DTP, VTP, and PAgP from using the default VLAN.

If there are access switch ports assigned to the default VLAN, this is a finding.

Fix Text (F-6925r298432_fix)
Remove the assignment of the default VLAN from all access switch ports.