The Cisco switch must have all trunk links enabled statically.
An XCCDF Rule
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.
- ID
- SV-220640r539671_rule
- Version
- CISC-L2-000200
- Severity
- Medium
- References
- Updated
Remediation Templates
A Manual Procedure
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