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Moved uplink module to a different switch won't work

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  • 1.  Moved uplink module to a different switch won't work

    Posted 12-30-2018 11:11


    Basically what i'm trying to do is replace a couple of EX3200 edge switches, each with their own fibre uplink module, with a stacked pair of EX4200s thus reducing the number of fibre connections to the core switch from 2 to 1. I have take the uplink module out of one of the EX3200s and put it into the master EX4200. I created a new IP address for accessing the new switch on vlan interface unit 0 and gave it a new host name. 


    I just can't get any IP connectivity to the core switch, nor from the core switch to the new edge switch. They do see each other as LLDP neighbours though. 


    As on the old switch I set a static route to the core using the routing-options command. 

    I also tried moving the SFP/fibre connector to a different slot on the uplink module.

    I made sure the link is set as trunk, with all vlans tagged and default as the native VLAN all on both ends of the connection exactly the same.

    I made sure the speed and duplex are the same and the link negotiation has completed. 

    Rebooted the switch.

    Nothing seems to work. When I ping the core I get 100% packet loss and likewise from the core to the new edge switch. I can ping the IP of the new switch locally though just fine.


    However as soon as I put the uplink module back into the old switch it works just fine.

    Happy to provide any further details.

    Any suggestions would be greatly appreciated!


  • 2.  RE: Moved uplink module to a different switch won't work
    Best Answer

    Posted 12-30-2018 13:12

    Just to update that I found the resolution.

    It looks like the reason was that I didn't link the layer to vlan to the layer 3 vlan interface. This KB pointed me in the right direction: https://kb.juniper.net/InfoCenter/index?page=content&id=KB11000

    I basically just assigned it to one of the (tagged/trunked) vlans I created.