The Cisco switch must have all disabled switch ports assigned to an unused VLAN.

It is possible that a disabled port that is assigned to a user or management VLAN becomes enabled by accident or by an attacker and as a result gains access to that VLAN as a member.

Step 1: Review the switch configurations and examine all access switch ports. Each access switch port not in use should have membership to an inactive VLAN.

interface Ethernet1/81 shutdown switchport access vlan 999

interface Ethernet1/82 shutdown switchport access vlan 999

interface Ethernet1/83 shutdown switchport access vlan 999

Step 2: Verify that traffic from the inactive VLAN is not allowed on any trunk links as shown in the example below:

interface Ethernet1/1 switchport mode trunk switchport trunk allowed vlan 1-998,1000-4094

Note: Switch ports configured for 802.1x are exempt from this requirement.

If there are any access switch ports not in use and not in an inactive VLAN, this is a finding.

Assign all switch ports not in use to an inactive VLAN.

Step 1: Assign the disabled interfaces to an inactive VLAN.

SW1(config)# int e1/81-128 SW1(config-if-range)# switchport access vlan 999 SW1(config-if-range)# end

Step 2: Configure trunk links to not allow traffic from the inactive VLAN.

SW1(config-if)# switchport trunk allowed vlan except 999 SW1(config-if)# end