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Dynamic Trunking Protocol and ports mode

zillah2004
Beginner
Beginner

((Dynamic Trunking Protocol (DTP), as the name implies, is the protocol used to automatically negotiate a trunk link.

DTP supports the auto negotiation of both ISL and 802.1q.

By default all ports on the Catalyst 3550 are dynamic desirable ports which will aggressively attempt to negotiate trunking through DTP.

To disable DTP and the auto negotiation of trunking, issue the interface level command switchport

nonegotiate)).

1- How many trunk mode have we got ? one of them is negotiation,,,Do we have any other ?

2- "By default all ports on the Catalyst 3550 are dynamic desirable ports".

2/a- Are there any other mode for ports ?

2/b- Is this different form one type of switch to another type ?

3 Replies 3

amit-singh
Collaborator
Collaborator

Hi,

1.Diff trunk modes are on,off,desirable,negotiate.

2/a. Diff modes of ports are, access, trunk, dynamic desirable.

2/b. Yes,its different, as 2950's and 2900/3500xl, dont have the port modes as dynamic desirable and do not negotiate trunks.

HTH,

-amit singh

"1.Diff trunk modes are on,off,desirable,negotiate".

Does DTP decide which mode to be used (chose one out of 5)?

"2/a. Diff modes of ports are, access, trunk, dynamic desirable. "

does that mean the dynamic desirable can be either access or trunk port ?

I get confused between three different interface mode :

1- switchports----can be access and trunk ports

2- routed ports

3- switched-virtual interface

"2/b. Yes,its different, as 2950's and 2900/3500xl, dont have the port modes as dynamic desirable and do not negotiate trunks."

CCNP Multilayer Switching V3 2.5.4 Basics of Dynamic Trunking Protocol (DTP) Cisco says:

"Dynamic desirable (default mode on Catalyst 2950 and 3550)"

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