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DTP Negotiation for Dummies

Warning: there is nothing formal about this post, just a way to help me (and maybe you, who knows) remember DTP port states:

Dynamic Desirable: “Hey, I want to trunk and I’m letting everyone know” (3550’s are DD by default)

Dynamic Auto: “I want to trunk, but I’m not announcing it. BUT! I’ll answer DTP trunking requests” (3560’s are DA by default)

DD + DA = Trunk (And use ISL unless configured otherwise — assuming Cisco switches)

DD + DD = Trunk

DA + DA = No Trunk for You!

You can disabled DTP by either:

  1. Setting the interface to static access using the switchport mode access command
  2. Turn off DTP all together with switchport nonegotiate


This entry was posted on July 31, 2009 at 11:34 am and is filed under Layer 2 Technologies with tags , . You can follow any responses to this entry through the RSS 2.0 feed You can leave a response, or trackback from your own site.

2 Responses to “DTP Negotiation for Dummies”

  1. CC[NI]P Says:
    September 15, 2009 at 3:54 pm

    Another neat thing about nonnegotiate and DTP (or DISL) is a case covered in Kennedy Clark’s Cisco LAN Switching (page 544). If I have two VTP domains and I want to get a trunk going between the two, they won’t come up! Reason: different VTP domain name in the DTP/DISL request. How does one make this situation work? “on” or “nonnegotiate”.

    Kind of neat, figured I’d share.

    Reply
  2. EtherChannel Negotiation for Dummies « Cisco Certified Hell Says:
    March 12, 2010 at 1:44 pm

    [...] Negotiation for Dummies Similar to my post on DTP negotiation, this is just my way of remembering the nuances of EtherChannel [...]

    Reply

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