The Cisco switch must not use the default VLAN for management traffic.
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-220644 | SRG-NET-000512-L2S-000010 | CISC-L2-000240 | SV-220644r991852_rule | 2024-06-06 | 3 |
Description
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.
ℹ️ Check
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
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