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V-220667

CAT II (Medium)

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

Rule ID

SV-220667r991904_rule

STIG

Cisco IOS XE Switch L2S Security Technical Implementation Guide

Version

V3R2

CCIs

CCI-004891

Discussion

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.

Check Content

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 GigabitEthernet0/0
 switchport access vlan 999
 shutdown
!
interface GigabitEthernet0/1
 switchport access vlan 999
 shutdown
…
…
…
interface GigabitEthernet0/9
 switchport access vlan 999
 shutdown

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

interface GigabitEthernet1/1
 switchport trunk allowed vlan 1-998,1000-4094
 switchport trunk encapsulation dot1q
 switchport mode trunk

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.

Fix Text

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

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

SW3(config)#int range g0/0 – 9
SW3(config-if-range)# switchport access vlan 999

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

SW3(config)#int g1/1
SW3(config-if)#switchport trunk allowed vlan except 999