Check: CISC-L2-000230
Cisco NX OS Switch L2S STIG:
CISC-L2-000230
(in versions v2 r3 through v1 r0.1)
Title
The Cisco switch must have the default VLAN pruned from all trunk ports that do not require it. (Cat II impact)
Discussion
The default VLAN (i.e., VLAN 1) is a special VLAN used for control plane traffic such as Spanning-Tree Protocol (STP), Dynamic Trunking Protocol (DTP), VLAN Trunking Protocol (VTP), and Port Aggregation Protocol (PAgP). VLAN 1 is enabled on all trunks and ports by default. With larger campus networks, care needs to be taken about the diameter of the STP domain for the default VLAN. Instability in one part of the network could affect the default VLAN, thereby influencing control-plane stability and therefore STP stability for all other VLANs.
Check Content
Review the switch configuration and verify that the default VLAN is pruned from trunk links that do not require it. SW1# show interface trunk -------------------------------------------------------------------------------- Port Native Status Port Vlan Channel -------------------------------------------------------------------------------- Eth1/1 1 trunking -- Eth1/2 1 trunking -- -------------------------------------------------------------------------------- Port Vlans Allowed on Trunk -------------------------------------------------------------------------------- Eth1/1 1-998,1000-4094 Eth1/2 1-998,1000-4094 If the default VLAN is not pruned from trunk links that should not be transporting frames for the VLAN, this is a finding.
Fix Text
Step 1: Prune VLAN 1 from any trunk links as necessary. SW1(config)# int e1/2 SW1(config-if)# switchport trunk allowed vlan except 1, 999 SW1(config-if)# end Step 2: Verify VLAN 1 is not allowed on the trunk link. SW1# show interface trunk -------------------------------------------------------------------------------- Port Native Status Port Vlan Channel -------------------------------------------------------------------------------- Eth1/1 1 trunking -- Eth1/2 1 trunking -- -------------------------------------------------------------------------------- Port Vlans Allowed on Trunk -------------------------------------------------------------------------------- Eth1/1 1-998,1000-4094 Eth1/2 2-998,1000-4094
Additional Identifiers
Rule ID: SV-220692r539671_rule
Vulnerability ID: V-220692
Group Title: SRG-NET-000512-L2S-000009
Expert Comments
CCIs
Number | Definition |
---|---|
CCI-000366 |
The organization implements the security configuration settings. |
Controls
Number | Title |
---|---|
CM-6 |
Configuration Settings |