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

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.

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.

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