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Why did my port go down? [Was: Hello to all]

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  • Why did my port go down? [Was: Hello to all]

    Hi,
    In cat 6500 series, why physical interface goes shutdown mode when a cannel-group number assign to the interface?

    One side is desirable and other side is auto?

    in two diffrent blades as it is a VSS switch and ather is running as normal. all are CAT6500 series

    Thanks

  • #2
    Re: Why did my port go down? [Was: Hello to all]

    Hello,

    When does the physical interface go down? is it when you assign the interface a channel-group? Need a show-run for more information. Is this isolated to one specific port? Or any port you assign to the channel. Also, remember that an etherchannel is not active until you configure all ports on both sides. Another issue may be that if you configure more than 8 ports on the same channel, the next interface you configure will go to standby mode.

    Other things to look for:
    - Make sure the interfaces associated with the same channel run the same protocol (PAgP/LACP) and the same duplex.
    - Make sure the channel group is on (#: channel-group <channel number> mode on depending on your IOS)

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    • #3
      Re: Why did my port go down? [Was: Hello to all]

      Hi, thehobo,

      physical interface goes down right after the cannel-group asing to the interface and say noshut

      Im trying this with only two interface (one in each side)


      they are trunk ports.

      two gigabit ethernet ports peoperly configured for trunk

      when i see sh run int interface . is shows the shutdown.

      oneside configuration is channel-group 10 mode desirable while other side is channel-group mode auto.

      Im trying this with only two interface (one in each side)

      thank you

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      • #4
        Re: Why did my port go down? [Was: Hello to all]

        With port channels the port settings need to be the same on both sides. IE speed, duplex, encapsulation, native vlan if dot1q etc. When configuring port channels always shut down the ports on both sides, do the configuration and then bring them up. There can be issues with the order of operations regarding etherchannels. Sometimes if you configure one side and it comes up it looks at the other side and doesnt see a match and will put the ports in err-disabled state.Also I almost never use any kind of autonegotiation.

        channel-group 10 mode on

        verification:

        show etherchannel summ
        CCNA, CCNA-Security, CCNP
        CCIE Security (In Progress)

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