The Cisco switch must have all trunk links enabled statically.
An XCCDF Rule
Description
<VulnDiscussion>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.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>
- ID
- SV-220640r539671_rule
- Severity
- Medium
- References
- Updated
Remediation - 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