The Arista MLS layer 2 switch must have all disabled switch ports assigned to an unused VLAN.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-255980	SRG-NET-000512-L2S-000007	ARST-L2-000170	SV-255980r991774_rule	2025-02-20	2

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.

ℹ️ Check
Step 1: Review the switch configuration and examine all access switch ports. Verify the unused port is configured to be intentionally shut down and assigned to an inactive VLAN. switch(config)#sh run int eth8 interface Ethernet8 description PORT IS INTENTIONALLY SHUTDOWN switchport access vlan 999 shutdown switch(config)# Step 2: Verify traffic from the inactive VLAN is not allowed on any trunk links as shown in the example below: switch(config)#sh run int eth9 interface Ethernet9 switchport trunk native vlan 1000 switchport trunk allowed vlan 2-998, 1001-4094 switchport mode trunk switch(config)# If any access switch ports are not in use and not in an inactive shutdown, this is a finding. Note: Switch ports configured for 802.1x are exempt from this requirement.

ℹ️ Check

Step 1: Review the switch configuration and examine all access switch ports. Verify the unused port is configured to be intentionally shut down and assigned to an inactive VLAN. switch(config)#sh run int eth8 interface Ethernet8 description PORT IS INTENTIONALLY SHUTDOWN switchport access vlan 999 shutdown switch(config)# Step 2: Verify traffic from the inactive VLAN is not allowed on any trunk links as shown in the example below: switch(config)#sh run int eth9 interface Ethernet9 switchport trunk native vlan 1000 switchport trunk allowed vlan 2-998, 1001-4094 switchport mode trunk switch(config)# If any access switch ports are not in use and not in an inactive shutdown, this is a finding. Note: Switch ports configured for 802.1x are exempt from this requirement.

✔️ Fix
Configure all Arista MLS switch ports not in use to be shut down and assigned to an unused VLAN. Step 1: Configure all unused ports to be shut down and assigned to an unused VLAN. switch(config)#interface ethernet 9 switch(config-eth9)#shutdown switch(config-eth9)# description this port is intentionally shutdown switch(config-eth9)# switchport access vlan 999 Step 2: Configure any trunk links to exclude the unused VLAN. switch(config)# interface ethernet 10 switch(config-eth10)# switchport trunk native vlan 1000 switch(config-eth9)# switchport trunk allowed vlan 2-998, 1001-4094 switch(config-eth9)# switchport mode trunk

✔️ Fix

Configure all Arista MLS switch ports not in use to be shut down and assigned to an unused VLAN. Step 1: Configure all unused ports to be shut down and assigned to an unused VLAN. switch(config)#interface ethernet 9 switch(config-eth9)#shutdown switch(config-eth9)# description this port is intentionally shutdown switch(config-eth9)# switchport access vlan 999 Step 2: Configure any trunk links to exclude the unused VLAN. switch(config)# interface ethernet 10 switch(config-eth10)# switchport trunk native vlan 1000 switch(config-eth9)# switchport trunk allowed vlan 2-998, 1001-4094 switch(config-eth9)# switchport mode trunk