9 Replies Latest reply: Mar 21, 2012 6:50 PM by Pete Nugent RSS

    WLC DHCP settings

    clive

      Just started studying for my CCNA wireless exam. I'm using a remote lab for the first time but had trouble setting the WLC to provide an IP address to the AP. Also if multiple scopes are configured what setting points the client to its prefered scope...any help would be great...thanks

        • 1. Re: WLC DHCP settings
          sbjones

          Normally the AP gets its address from from a DHCP server and then does a subnet broadcast for WLCs. Your email suggests that there is no DHCP server on the network already providing IP addresses and that you need the WLC to do it.

           

          To configure the controller as a DHCP server, in the controller GUI go to:

          CONTROLLER > Internal DHCP Server > New

          (Controller is one of the tabs on the horizontal menu)

           

          Here are some sites that may help:

           

          --Cisco guide to Configuring DHCP and DHCP scopes here:

          http://www.cisco.com/en/US/docs/wireless/controller/5.1/configuration/guide/c51wlan.html#wp1152559

           

          --For info on the AP to WLC join process here:

          http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a00806c9e51.shtml?referring_site=bodynav

           

          --Using DHCP Option 43 (only needed if your AP is on a different subnet than the WLC) here:

          http://www.cisco.com/en/US/tech/tk722/tk809/technologies_configuration_example09186a00808714fe.shtml

          • 2. Re: WLC DHCP settings
            Drobba

            Not really sure what you mean when you ask "if multiple scopes are configured what setting points the client to its prefered scope...any help would be great...thanks " 

            If your in a lab enviroment you could build a scope off your managment interface and reserve a range for your mgt devices and a range for your APs.  SBJones has provided a great links to start off with if your building scopes for muiltiple SSIDS.

            • 3. Re: WLC DHCP settings
              clive

              Thanks to both for your help, yes there was no other dhcp server but as I couldn't get the WLC to offer an address I set one up on the switch everything on the same subnet so option 43 was not needed. I guess where I'm getting confused is on the link from SB...

               

              Step 7 In the Network field, enter the network served by this DHCP scope. This is the IP address used by the management interface with Netmask applied, as configured on the Interfaces page.

               

              This implies I have to put a network address into the relevant interface dhcp field, I would have expected to have put a dhcp server host address here.

               

              I cant try this again until I book some more lab time...but thanks again.

              • 4. Re: WLC DHCP settings
                chris reynolds

                clive wrote:

                 

                Thanks to both for your help, yes there was no other dhcp server but as I couldn't get the WLC to offer an address I set one up on the switch everything on the same subnet so option 43 was not needed.

                 

                 

                Had you tried putting the controllers IP address as the primary DHCP server on that Interface?

                • 5. Re: WLC DHCP settings
                  clive

                  Yes but think I know where I was going wrong now that I've managed to get a look at a working config. You do put the IP address of the managemen tinterface as the dhcp server address on the interface but you also have to put one of the reserved addresses from the scope you want to use along with the same gateway address...this links the scope (which might be one of a many) to that interface....I think!

                  • 6. Re: WLC DHCP settings
                    sbjones

                    That makes sense except that I don't think you would use one of the addresses from the scope. I think it would be the reserved network address for the scope and its mask.

                     

                    For example if you wanted to reserve addresses from the 10.1.1.16/28 network:

                     

                    The pool start address would be 10.1.1.17

                     

                    The pool end address would be 10.1.1.30

                     

                    = 14 useable addresses not including the network number itself (10.1.1.16) and the broadcast address (10.1.1.31).

                     

                    The network would be 10.1.1.16

                     

                    The net mask 255.255.255.240

                    • 7. Re: WLC DHCP settings
                      clive

                      Looking at the working config copy I've got its definately a host address from the scope reserved range, I'm going to try it on the lab session I've booked this weekend.

                      • 8. Re: WLC DHCP settings
                        sbjones

                        A host address might work, with the mask it will identify the network but a host address is not a network address, it identifies a single machine or interface on a network. The GUI asks for a network not a host or interface IP. I will be curious to see the results of your lab. See this thread:

                        http://www.techsupportforum.com/forums/f31/solved-setting-a-dhcp-scope-on-cisco-2125-wireless-lan-controller-392156.html

                        • 9. Re: WLC DHCP settings
                          Pete Nugent

                          The address does not need to be in the scope just in the same subnet.

                           

                          So if you were using VLAN 20 for example and set a scope up as 192.168.1.10 - 200 and a network mask of 255.255.255.0 so a 24 bit mask. Any address, with the  exception of the broadcast address could be used like 192.168.1.5 for the dynamic interface. Remember the scope may only be a part of the whole subnet. If its a reserved address thats fine aswell but I dont see the point of creating a scope and then adding reserved addresses, Just leave them outside the scope and asign them as static addresses, same result at the end I guess.