5 Replies Latest reply: Dec 17, 2012 4:30 PM by Paul Stewart - CCIE Security RSS

    What Trunking port Does?

    Bart

      I was told to setup trunk for vlan x on which bunch of AP's was connected to.  According to cisco documents trunking ports allows vlans to talk to each other.  I don't undertand how this could be related to AP's? In common sense why do I need to trunk ports on vlan x(where aps are) to have it working?  any ideas?

        • 1. Re: What Trunking port Does?
          Justin G

          I’m not sure on the context on which you were requested to create the trunk, but a trunk provides a means to carry multiple VLANs across a single network link.

           

          With this in mind, it’s not un-common to set the interconnections to WAPs as trunks as multiple ssid’s may be defined on the WAP, all corresponding to different VLANs. Don’t forget the management VLAN as the BVI ip address may be within another VLAN.

           

          I’m just guessing, but was the request to add VLANx into the allowed list across the link existing WAPs?

          • 2. Re: What Trunking port Does?
            Jared

            Trunking ports don't allow vlans to talk to each other.  That is the job of a layer 3 device.  A trunk port would allow multiple vlans on a single port Justin stated.

             

            If you have an autonomous AP that has multiple SSIDs, Each of those SSIDs would map to a different vlan.  The AP has only one ethernet interface so you would need to configure it as a trunk port so all of the different vlans would pass from the AP to the switch.

            • 3. Re: What Trunking port Does?
              Bart

              "The AP has only one ethernet interface so you would need to configure it as a trunk port so all of the different vlans would pass from the AP to the switch."

               

              -this is what I was looking for (was confused).  To make it logical, making it as trunk is like a highway with let say 5 lanes one way VS. as access only one allowed at a time? - does it make sense?.

               

              Going to Justin confusion, this was my first day of work so I can't remember exactly whole scenario but there was x amount of AP's connected to vlan 50 which were not trunked. Setting switchport mode trunk did the justice.

              • 4. Re: What Trunking port Does?
                Bart

                trunking still doesn't make sense for me.  I've found articles of what trunking is but I still don't see the use of it besides connecting two switches together.-

                "A trunk can be a link between two switches, a switch and a router, or a switch and a server. Trunks support traffic for multiple VLANs and allow the administrator to extend VLANs across multiple switches."

                What I don't understand is what do they mean by "TRUNKS SUPPORT TRAFFIC FOR MULTIPLE VLANS".  -  So let say i.e I have 5 Ap's on VLAN 99.  besides I have VLAN 20(printers), VLAN 30(PC's) - why would I trunk VLAN99? I know this may sound stupid for some of you but I just can't get the logic behind it for some reason.... Please help

                • 5. Re: What Trunking port Does?
                  Paul Stewart  -  CCIE Security

                  The normal recommendation from Cisco is to trunk down to autonomous AP's and create access ports for Lightweight AP's. The reason for the recommendation is so multiple SSIDs can be used and mapped to different VLANs. If all of your wireless clients have the same need, one SSID can be used and the switchport can be an access port. Lightweight AP's do it differently. Basically, all of the traffic is tunneled back to the controller. HTH.