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V-101151

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

Finding ID
CISC-L2-000220
Rule ID
SV-110255r1_rule
Severity
Cat II
CCE
(None)
Group Title
SRG-NET-000512-L2S-000008
CCI
CCI-000366
Target Key
(None)
Documentable
No
Discussion

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.

Fix Text

Remove the assignment of the default VLAN from all access switch ports.

Check Content

Review the switch configurations and verify that no access switch ports have been assigned membership to the default VLAN (i.e., VLAN 1). VLAN assignments can be verified via the show vlan command: SW1#show vlan VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active 10 User VLAN active Gi0/3, Gi1/0, Gi1/1, Gi1/2 Gi1/3, Gi2/1 20 Management VLAN active Gi0/2 999 VLAN0999 active Gi2/0 If access switch ports are assigned to the default VLAN, this is a finding.