The layer 2 switch must have all trunk links enabled statically.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-206665	SRG-NET-000512	SRG-NET-000512-L2S-000005	SV-206665r385561_rule	2025-03-05	3

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.

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.

ℹ️ Check
Review the switch configuration to verify that trunk negotiation is disabled by statically configuring all trunk links. Configuring a command to manually disable negotiation may also be required for some switch platforms. If trunk negotiation is enabled on any interface, this is a finding.

✔️ Fix
Configure the switch to enable trunk links statically.