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V-220644

CAT II (Medium)

The Cisco switch must not use the default VLAN for management traffic.

Rule ID

SV-220644r991852_rule

STIG

Cisco IOS Switch L2S Security Technical Implementation Guide

Version

V3R1

CCIs

CCI-004931

Discussion

Switches use the default VLAN (i.e., VLAN 1) for in-band management and to communicate with directly connected switches 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.

Check Content

Review the switch configuration and verify that the default VLAN is pruned from trunk links that do not require it:

SW1#show interfaces trunk

Port Mode Encapsulation Status Native vlan
Gi0/1 on 802.1q trunking 1
Gi0/2 on 802.1q trunking 1

Port Vlans allowed on trunk
Gi0/1 1-998,1000-4094
Gi0/2 1-4094

If the default VLAN is not pruned from trunk links that should not be transporting frames for the VLAN, this is a finding.

Fix Text

Configure the switch for management access to use a VLAN other than the default VLAN:

SW1(config)#int vlan 22
SW1(config-if)#ip add 10.1.22.3 255.255.255.0
SW1(config-if)#no shut