Port behavior when configured for both access & trunk

[zagato_79]

Can someone help me understand how the switch port behaves when a port is configured for access port as well as trunk port.

int gi1/3

Switchport

switchport access vlan XX

switchport mode trunk

Switchport trunk enca dot1q

switchport trunk allowed vlan YY,ZZ

If the trunk fails for any reason will the port will changes its behavior to access port? In the above configs the command mode trunk will override the behavior of access port to trunk port , and to my knowledge unless you change mode “no switchport mode trunk" we cannot change the behavior of the port to access mode. let me know if my understanding is correct or not.

Thanks

[Leo Laohoo]

You can't have a single port act as an access port AND a trunk port. You can only have one. The configuration line which determines which is which is "switch port mode trunk" or "switch port access vlan XX".

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[zagato_79]

Thanks for your reply, I understand the port cannot be BOTH,That's what I mentioned in my post as well.my question was "If we have both configs and if the trunk fails for any reason will the port changes its behavior to access port automatically ??" with out human intervetion or with out converting port back to access port by using the command no switchport mode trunk

[John Blakley]

As Leo stated, your mode is strictly configured for a trunk which means that you won't be able to fail over to an access port. You can however have the port configured for dynamic which will try to form a trunk. If that fails, then it will fall over to an access port on the vlan that you have configured on the port.

HTH,
John

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[Wilson Bonilla]

Hi.

"If we have both configs and if the trunk fails for any reason will the port changes its behavior to access port automatically ??

To keep it simple: the answer is NO!!!

The best you can do configure the port as dynamic desirable.

Switch(config-if)#switch mode dynamic desirable

Regards.

Wilson B.

[bonnardopjl]

Hi,

This is needed when DTP (Dynamic Trunk Protocol) is active.

Suppose you do not have "switchport mode runk", then DTP will try

to negotiate with the other device if the interface is "access" or "trunk".

This negotiation take about 2 sec.

Because I think this is very dangerous, I allways configure the

some "switchport mode ..." an in addition

"switchport nonegotiate" in order to disable DTP.

Then the DTP do not loose 2" to negotiate nothing.