Using DTP on a port-channel
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05-24-2016 09:35 AM - edited 03-08-2019 05:55 AM
Hi,
I have a simple question.
I've tried to configure a port-channel between two switches. But it seems that it's not possible to configure dtp on the port-channel.
The channel is well configured but I can't make the trunk working with "switchport mode dynamic auto" (or desirable) on the interface port-channel.
I mean I can enter the command but the channel doesn't transmit the frames and the channel doesn't work properly.
Is it normal?
Thanks.
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05-24-2016 09:57 AM
Jeremy,
I would need to test this in a lab as I personally avoid DTP as much as possible - but that, of course, does not mean you should not try it out!
Before I do that, though, can you please answer the following questions for me?
- Where exactly did you configure the switchport mode dynamic command - did you enter it on the physical ports or on the Port-channel virtual interface? It should be placed on both.
- What does the show etherchannel summary command on both switches say? Does it show the Port-channel interface as SU (Switched, Up) with all physical ports marked with P (In Port-channel)?
- What does the show interfaces trunk say? Especially if you configure at least one of the switches with switchport mode dynamic desirable, does the show int trunk show the Port-channel being treated as a trunk?
Best regards,
Peter
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05-24-2016 12:47 PM
Thanks for your reply.
I try it with Packet Tracer and I think pkt is the problem.
It works perfectly when I put the trunk mode as "on". But it's completely bugging when using desirable on the port-channel and physical interfaces (interfaces shutting down, then upping, then trunking on/off, ...). And the trunk is not mounting when one side is desirable and the other auto.
So I think it's packet tracer, but thanks to tell me it could work.
NB : I know DTP shouldn't be used, but that's for my personal knowledge ;)
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05-31-2016 01:59 AM
Seems that trunking mode has to be the same between etherchannel interfaces.
Look at the answer of a netacad quiz question I've done (on the attachment).
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05-24-2016 09:57 AM
No it should work. One end should be auto and the other dynamic or both ends should be dynamic . Maybe post your config.
