VLAN 1 must not be used for user VLANs.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-3971	NET-VLAN-004	SV-3971r2_rule		Medium

Description
In a VLAN-based network, switches use VLAN 1 as the default VLAN for in-band management and to communicate with other networking devices using Spanning-Tree Protocol (STP), Cisco Discovery Protocol (CDP), Dynamic Trunking Protocol (DTP), VLAN Trunking Protocol (VTP), and Port Aggregation Protocol (PAgP)--all untagged traffic. As a consequence, VLAN 1 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 VLAN 1 as the default VLAN for in-band management and to communicate with other networking devices using Spanning-Tree Protocol (STP), Cisco Discovery Protocol (CDP), Dynamic Trunking Protocol (DTP), VLAN Trunking Protocol (VTP), and Port Aggregation Protocol (PAgP)--all untagged traffic. As a consequence, VLAN 1 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
Infrastructure L3 Switch - Cisco Security Technical Implementation Guide	2017-09-28

Details

Check Text ( C-4028r3_chk )
Review the device configuration and verify that access ports have not been assigned membership to the VLAN 1. If any access ports are found in VLAN 1, this is a finding.

Fix Text (F-3904r2_fix)
Best practices for VLAN-based networks is to prune unnecessary ports from gaining access to VLAN 1 as well as the management VLAN, and to separate in-band management, device protocol, and data traffic.