Does VTP domain matter if "switchport mode trunk"?

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Feb 4th, 2008
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If I have two switches with trunks in between, assuming I configure the trunk ports on both switches as "switchport mode trunk". would the trunk come up if the VTP domain names are dfferent on two swtiches?


Thanks

Gary

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s.arunkumar Mon, 02/04/2008 - 21:17
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hi

I think "switchport mode trunk" alone configured will still send dtp messages.hence u need to configure "switchport nonegotiate" in this case..


arun



gwhuang5398 Mon, 02/04/2008 - 21:25
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If I don't configure any "vtp domain ..." statement, would that solve the problem or not work at all?


Gar

shrikar.dange Mon, 02/04/2008 - 21:43
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hi,


If you do not configure any domain name on both switches then the doamin name used will be blank.In this case the trunk should come up.


HTH,


regards,


shri :)

s.arunkumar Mon, 02/04/2008 - 22:09
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Yes as above said the for DTP to make the trunk up the VTP domain should be same ,or one or both end should be NULL(by default)..


arun

aijaz802 Tue, 02/05/2008 - 00:48
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Hi,


Trunk will come up and works fine even if the vtp domain names are different and in diff modes. I have tested....

shrikar.dange Tue, 02/05/2008 - 02:04
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hi,

AFAIK while using DTP negotiations the VTP domain name is checked and if unmatched the trunk will not came up.If you configure the trunk as nonegotiate then the domain name is not considered.


HTH,


regards,


shri :)

gwhuang5398 Wed, 02/06/2008 - 20:51
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Thanks all for the help. I think if DTP is not involved in the trunk establishing process, then VTP domain name does not matter. I somehow have the impression that if the port mode is set to "trunk", DTP will not have negotiation between the two interfaces, so the trunk would come up regardless. Please let me know if I misunderstood it.


Gary

s.arunkumar Wed, 02/06/2008 - 21:16
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As i understand the DTP messages are still send evenif u configure mode to "trunk" only..


The dtp messesages are stopped only with "nonegogiate" option


arun

glen.grant Thu, 02/07/2008 - 00:44
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If you run switchport mode trunk with the nonegotiate option then the vtp domain names do not matter as dtp frames will not be sent . If you configure them to dynamically create the trunks with the option switchport mode dynamic desirable or auto then the vtp domain names do matter and the trunk will not come active unless they match. That being said if you force them on all the switch has to see is a physical link and it will say it is trunking when it might not be if configured incorrectly so that is the danger of forcing them on . When you use dynamic trunk protocols this problem is eliminated.

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