The Cisco switch must have all trunk links enabled statically.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-220640 | CISC-L2-000200 | SV-220640r539671_rule | CCI-000366 | medium |
| Description | ||||
| When trunk negotiation is enabled via Dynamic Trunk Protocol (DTP), considerable time can be spent negotiating trunk settings (802.1q or ISL) when a node or interface is restored. While this negotiation is happening, traffic is dropped because the link is up from a Layer 2 perspective. Packet loss can be eliminated by setting the interface statically to trunk mode, thereby avoiding dynamic trunk protocol negotiation and significantly reducing any outage when restoring a failed link or switch. | ||||
| STIG | Date | |||
| Cisco IOS Switch L2S Security Technical Implementation Guide | 2024-06-06 | |||
Related Frameworks
4 paths across 3 frameworks
Related Frameworks
NIST 800-531 mapping
CM-6
1.00
- DISA · V3R1 · disa_xccdf · related
- DISA · 2025-01-23 · disa_cci_list · equivalent
NIST 800-1712 mappings
3.4.1
1.00
- DISA · V3R1 · disa_xccdf · related
- DISA · 2025-01-23 · disa_cci_list · equivalent
- NIST · Rev 2 (Feb 2020, errata Jan 2021) · nist_800_171_app_d · equivalent
3.4.2
1.00
- DISA · V3R1 · disa_xccdf · related
- DISA · 2025-01-23 · disa_cci_list · equivalent
- NIST · Rev 2 (Feb 2020, errata Jan 2021) · nist_800_171_app_d · equivalent
CCI1 mapping
CCI-000366
1.00
- DISA · V3R1 · disa_xccdf · related
Details
Check Text (C-220640r539671_chk)
By default, DTP is enabled on all Cisco switches. Review the switch configuration to verify that trunk links will not form a trunk via negotiation as shown in the example below:
SW2#show interfaces switchport
Name: Gi0/0
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: static access
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
If trunk negotiation is enabled on any interface, this is a finding.
Fix Text (F-22344r507967_fix)
Configure the switch to enable trunk links statically as shown in the configuration below:
SW2(config-if)#switchport trunk encapsulation dot1q
SW2(config-if)#switchport mode trunk
SW2(config-if)#switchport nonegotiate