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Beginner

create a dot1q trunk between 4500X and ME3600X

Hi There,

today during an initial configuration of a network i came to a simple issue. supposed to be simple :-)

When i set up a trunk between ME3600X and 4500X i failed.

ME is not supporting "desirable" and so in need to set up the trunk in mode "on" there.

On the other side desirable is supported, however i were not able to establish a working trunk.

When i initally set up the trunk I configured in desirable mode on 4500X --> failed

When i set trunking to on the devices tells me that this port is trunking, however in fact the trunk is still not working.

After this i changed config back to desirable and the 4500X shows me the port "trunking" but in fact trunking is still not working.

config is as followed:

on ME3600X:

int gi0/20

switchport trunk allowed vlan 25-27,30,31,40

switchport mode trunk

on 4500X

int te1/32

switchport trunk allowed vlan 25-27,30,31,40

switchport mode dynamic desirable

Has anyone an idea what could be wrong there. The link status is up / up

Is there some sort of best practise trunk configuration for my setup available?

Thanks for your assistance in advance

3 REPLIES 3
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Rising star

You said that the ME doesn't support the 'switchport mode dynamic desirable' command.

What would happen if on the 4500X you configured the following

int te1/32

switch mode trunk

swich trunk allowed vlan 25-27,30,31,40

Basically, 'dynamic desirable' is using DTP . It's basically saying, hey I want to negoitate a trunk with you, and if it can't it reverts to an access port. But 'dynamic desirable and mode trunk' should be availabel to form a trunk...

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If i do a switchport mode trunk the status chages to "trunking", however in fact the trunk is still not working.

And the cracy thing is when i switch back from "switchport mode trunk" to "switchport mode dynamic desirable" trunk remains up, but is still not working.

Highlighted

Hi.
Can you post a show interface trunk of both switch?
Thanks

Regards
Carlo

Sent from Cisco Technical Support iPhone App

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