Cisco DTP (Dynamic Trunking Protocol) Notes

Posted by keith.wirch at August 17, 2017

Category: CCNP Notes

This will put the interface in a permanent non-trunking mode.  With exception of a Voice VLAN, only one vlan will pass over this port.  The port will NEVER become a trunking port.

This will put the interface in a permanent trunking mode.  Allowed VLANs allowed on the trunk will pass.  VTP will also pass traffic over this port.  DTP packets will be sent to ask the other side to become a trunk.  If the other side does not respond, the port will become a trunk anyway.

This will cause the interface to not send DTP packets.  Meaning that it will not attempt to negotiate as a trunk.  But if the port does receive a DTP packet that it wants to become a trunk, it will become a trunk.

Dynamic Desirable
When a port comes up with this configuration, it will ask the other side “Hey, wanna be a Trunk?”.  In other words, it will actively try to be a trunk.  But it will cause port to the function of an access port if needed.

Dynamic Auto (DEFAULT)
In this configuration, the port will become a trunk if asked to but otherwise just stays a regular access port otherwise.

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