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


Overview

Finding ID Version Rule ID IA Controls Severity
V-101251 CISC-L2-000210 SV-110355r1_rule Medium
Description
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.
STIG Date
Cisco NX-OS Switch L2S Security Technical Implementation Guide 2020-05-07

Details

Check Text ( C-100131r1_chk )
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.
Fix Text (F-106955r1_fix)
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