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Home Forums How to configure trunk on Cisco Catalyst Switch

This topic contains 36 replies, has 21 voices, and was last updated by   Amjed A 2 weeks ago.

Viewing 15 posts - 1 through 15 (of 36 total)
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  • #15319


    You have a very unique way of explaining, Clear and direct to the point. I am very grateful.
    Thank you


    kareem mohamed

    I really appreciate your efforts 🙂



    Hi ,
    Im following you LAB but i would like to know how to change the Operational Mode
    status .
    Every times i would like to change it , it doesn’t work .

    #sh int Fa0/21 switchport
    Name: Fa0/21
    Switchport: Enabled
    Administrative Mode: trunk
    Operational Mode: down <—
    Administrative Trunking Encapsulation: dot1q
    Negotiation of Trunking: Off
    Access Mode VLAN: 50 (TesteIMO(NOTOUCH))
    Trunking Native Mode VLAN: 1 (default)
    Voice VLAN: none

    Thanks for your help .


    bharathi n

    Can u check whether u made it no shut?



    Please clarify how to interpret the table you listed in the page below with different modes


    Rene Molenaar

    The horizontal values are for “switch 1” and the vertical values for “switch 2”.

    For example, if you use “dynamic auto” on switch 1 and 2 then the result will be access mode.


    Srinivasan C

    Hi Rene,
    Network operators knows which ports are connected to switch and hosts. They can configure access mode or trunk mode accordingly.
    Why do we need Dynamic access and Dynamic auto ? In what scenario we use it in
    production network?



    Rene Molenaar

    Hi SV,

    I can’t think of any good reason to use dynamic auto or desirable. It’s best always to use static access or trunk mode.



    Srinivasan C

    Hi Rene,
    Thanks for your quick reply!




    Rene, question, on your last compare example, its static access and static trunk, the result was trunk on both sides, so its a working trunk port? but on your table that you created, the Static Trunk and Static Access has a “Limited” value. care to explain why its Limited? and what does it do on the switch?


    Rene Molenaar

    Hi John,

    When you mix access and trunk mode, we get to see this message:

    %SPANTREE-7-RECV_1Q_NON_TRUNK: Received 802.1Q BPDU on non trunk FastEthernet0/14 VLAN1.
    %SPANTREE-7-BLOCK_PORT_TYPE: Blocking FastEthernet0/14 on VLAN0001. Inconsistent port type.
    %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking FastEthernet0/14 on VLAN0001. Port consistency restored.

    The trunk will send BPDUs for each VLAN, our access mode interface only sends one BPDU so that’s why CDP reports this error. This won’t be a working trunk but I think the access mode VLAN (VLAN1) will work.

    I’d have to give this a try to see if it works.



    Faisal A

    Thanks .

    It’s awesome.


    Donald S


    how do you turn trunk negotiation back on?


    Rene Molenaar

    Hi Donald,

    “switchport nonegotiate” disabled it and “no switchport nonegotiate” enables it again.



    Inderpal K

    Hi Rene

    Please can you advise what I can do, I am trying to create vlan 50 on this switch and keep getting following

    SW1(config)#vlan 50
    VTP VLAN configuration not allowed when device is not the primary server for vlan database.
    SW1#sh vtp status
    VTP Version : 3 (capable)
    VTP version running : 3
    VTP Domain Name : CCIE-domain
    VTP Pruning Mode : Disabled (Operationally Disabled)
    VTP Traps Generation : Disabled
    Device ID : aabb.cc00.0700
    Feature VLAN:
    VTP Operating Mode : Server
    Number of existing VLANs : 8
    Number of existing extended VLANs : 0
    Configuration Revision : 0
    Primary ID : 0000.0000.0000
    Primary Description :
    MD5 digest : 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
    0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
    Feature MST:
    VTP Operating Mode : Transparent
    Feature UNKNOWN:
    VTP Operating Mode : Transparent


    I tried deleting vlan.dat but to no avail






Viewing 15 posts - 1 through 15 (of 36 total)

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