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eesun_276598's avatar
eesun_276598
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Dec 06, 2017

VLAN ID and tag

Hi Anyone can make it clear the concept with relation between VLAN ID and its tag in f5. In Cisco switch, vlan id is vlan number, such as vlan 10, vlan 20, vlan 30 etc. And tag is used when two switc...
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eesun_276598's avatar
eesun_276598
Icon for Cirrus rankCirrus
Dec 11, 2017

So, when we configure vlan, we could have two choices, one is tagged and other is untagged interface. For example, the tag is 10, then we put it under untagged interface 1.1, the tag 10 means vlan10 will be created, but why we have choice to put it under untagged interface? That would remove tag 10? or if so, what that means after removing tag10? Thank you

 

  • Gonzalex_330537's avatar
    Gonzalex_330537
    Icon for Cirrostratus rankCirrostratus
    Dec 14, 2017

    Basically, strictly within the networking concept itself, you can have trunk interfaces (tagged ports) and access ports (untagged ports).

     

    When you specify a tag of X, vlan X is created. What dictates further the choice of tagged vs untagged is the device and configuration at the other end of the link.

     

    So you could then have two cases:

     

    a) The port is tagged - meaning, it is a trunk port. Furthermore, it accepts incoming tagged frames and tags frames before sending them out. You setup a trunk port if your F5 connects to another trunk port - normally on another switch. In this configuration you are basically aggregating traffic from all vlans, on a single port.

     

    b) The ports is untagged - in this case, you are configuring an access port in vlan X - simple as that. You could have more than one port in the same VLAN - think of it as a switch with more than one port in the same vlan ... so hosts connected to those two ports can communicate directly as they will be in the same broadcast domain. Unlike with trunk ports, here you are segregating the traffic into multiple vlans.

     

  • eesun_276598's avatar
    eesun_276598
    Icon for Cirrus rankCirrus
    Dec 18, 2017

    I agree on this comment. but in your first comment, you mentioned " Vlan ID and VLAN tag are the same thing - not only in F5 but across all vendors. This is a networking concept not bound to a specific vendor". "tag" should be concept regarding trunk port. Only when frame enter trunk port, the tag will be added to the frame. While VLAN ID is vlan mark, which identify different vlan. How can you say the two are the same things? Can you explain? Thank you