If i configure a switch to use switchport mode trunk with no negotiate command , would that form a trunk with the other end switch which is configured to act in dynamic mode auto ? Also I am looking for the reason, how could switches configured as "trunk" / ON mode , could form trunk even when we disable DTP on them. What kind of communication happens between the switches in trunk mode to let them bring up a trunk link, when dtp frames are disabled ?
When you put a switchport into trunking mode, it will trunk and it will try to negotiate. Dynamic auto will wait for a request to trunk, so if the other side is set to trunk, a trunk will form. If you disable negotiating by issuing the switchport nonegotiate command, both sides will need to be set to trunk in order for a successful trunk to be created.
When both sides are configured to trunk, no negotiation is needed. A trunk will be formed based on the manual configuration of the switches and the switchports.
DelVonte nailed it.....
When you configure nonegotiate, you're disabling DTP - but not the port's ability to function as a trunk. With DTP disabled the port will behave as dictated by the manual configuration you enter.
Thanks for the information Guys.
So to let the switches to bring up a trunk, given a condition that one of the switch is configured for dynamic mode (auto / desirable), it requires the dtp to be enabled (on both the switches) irrespective of the mode (either trunk / auto / desirable) that is configured on far-end switch. Did i grasp it correctly ?
In order to negotiate a trunk, both switches do need to have DTP enabled, but If your switchport is in dynamic auto mode, the other side needs to be in either dynamic desirable or trunk in order for a trunk to form successfully. Other than that, you are correct.