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24256 Views 4 Replies Latest reply: Aug 19, 2012 6:31 PM by middlelord RSS

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configuring a trunk port

Mar 22, 2013 10:12 AM

Steverino 375 posts since
May 3, 2010

How do you configure a trunk port?

  • Paul Stewart  -  CCIE Security, CCSI 6,989 posts since
    Jul 18, 2008
    Currently Being Moderated
    1. May 15, 2010 3:56 PM (in response to Steverino)
    Re: configuring a trunk port

    Just a basic configuration would be.


    interface Fa0/1

    switchport trunk encapsulation dot1q

    switchport mode trunk


    Some switches only support one encapsulation type on a trunk.  In that case, there is no command "switchport trunk encapsulation dot1q".  Some older Cisco stuff only done the proprietary ISL trunking.  Now most switches do the standard dot1q or both methods.

  • Keith Barker - CCIE RS/Security, CISSP 5,351 posts since
    Jul 3, 2009
    Currently Being Moderated
    2. May 15, 2010 4:09 PM (in response to Steverino)
    Re: configuring a trunk port

    Paul's answer is right on the money.


    If you are using Packet Tracer, it may not support the command switchport trunk encapsulation dot1q, but will still use it as a default.   You will still be good to go if you use the switchport mode trunk command.


    Best wishes,



  • Angela 746 posts since
    Jan 29, 2010
    Currently Being Moderated
    3. May 15, 2010 11:57 PM (in response to Steverino)
    Re: configuring a trunk port

    Just adding a little note here, if you wish to configure an ISL trunk, use 'switchport trunk encapsulation isl' instead.


      Also, if you want to create a trunk link between a switch and a router, you only need to configure trunk on the switch MANUALLY because the router doesn't know what is trunking....




  • middlelord 3 posts since
    Jun 23, 2009
    Currently Being Moderated
    4. Aug 19, 2012 6:31 PM (in response to Angela)
    Re: configuring a trunk port

    I think trunking has to be setup on the router port that connects to the trunking port of the switch.


    On the Cisco ASR 1002 router you would have to create a sub interface and configure the dot.q trunking on it. then configure the ip addresses of the sub-interface for each vlan.


    Have a great day!


    Scott Alvarino



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