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SP_266134's avatar
Icon for Nimbostratus rankNimbostratus
Jan 12, 2018

VLAN Tagged vs Untagged. What does this mean.

I have two interfaces 1 and 2 and decided to use 1 for internal traffic and 2 for external traffic. Both Vlan and untagged. Should one be tagged or not. I don’t see any communication from the External vlan TCPDump . I don’t get any communications TCPDump on the external vlan arp. What exactly does this mean.


4 Replies

  • Tagged means the VLAN dot1q header is going to be added to the frame and sent to the downstream device. This is normally done to trunk interfaces (Cisco terminology "Trunk") on a switch so it knows what VLAN the frame belongs to.


    Untagged means the frame gets sent out the port with no VLAN information. You would do this on an access port (Cisco terminology)


    Normally, you will probably set both of these as tagged interfaces so you can use multiple VLANs per interface instead of building a new interface for each and every VLAN if it was an untagged interface.


    • SP_266134's avatar
      Icon for Nimbostratus rankNimbostratus

      Thanks . you recommend both interfaces should be tagged. i will change them accordingly.


  • Surgeon's avatar
    Ret. Employee

    If your adjacent switch has tagging then you need to add tagging on the big-ip interface, otherwise you need to leave it as untagged.


  • Assume if i have router and F5 connected in this case would you suggest to keep as an untagged or tagged?