2 Replies Latest reply on Jul 14, 2015 6:14 PM by zprime

    Temporarily disable DHCP server without removing/altering pools?

    zprime New Member

      I think the subject says it all... is there any way to temporarily disable DHCP on one or more interfaces without removing the DHCP pools entirely?

       

      I know that I can "no ip dhcp server pool POOLNAME", but that then means I have to recreate the entire pool from scratch when I want to re-enable DHCP again.

       

      The situation here is that I'm dropping a router into a network that currently has a different IP range and is using a different router for internet access.  I have a PC in that network configured with a secondary (static) IP address so it will be able to talk to this new router, but I don't want the new router assigning DHCP to the rest of the network just yet (the T1s it is handling need to be tested first).

       

      The new router has two subinterfaces (separate VLANs) and I need to disable DHCP server on both of those.

       

      I'm trying to avoid "no-ing" both pools and having to re-add them later because each pool has a bunch of dhcp-options that I would have to re-add as well.

       

      On a Cisco, I believe it's possible to "no service dhcp server" or something along those lines to temporarily disable the server, without losing the config options.  I'm looking for something similar - in this case, there are no interfaces / subnets that need a functional server (I don't need to selectively disable single interfaces or pools, I just need to shut off all DHCP serving from this router for a day or two).

       

      I suppose I could simply add the entirety of both pools as excluded-addresses, but I worry then that the DHCP server will still try to reply to client requests, which I don't want (there's another DHCP server on the network that will be turned off once the T1s are ready and I can re-enable DHCP on the Adtran).

       

      The Netvanta happens to be a 3305 on base firmware here, but I suspect this would apply to all AOS... It's on the latest long-term / maintenance release (R11.4.3).

       

      My other alternative would be to backup the current config (with DHCP pools enabled), and then alter and save it as startup without the pools.  Once the T1s are tested and functioning, I can copy <backupconfig> running-config and that should get the pools back, but I've seen strangeness when copying a stored config into the running (it seems like copying to startup-config and rebooting is safer, but I'm trying to avoid the reboot as well as having to re-add the pools by hand).

        • Re: Temporarily disable DHCP server without removing/altering pools?
          cj! Beta_User

          Hi zprime:

           

          This is a great question.  You could block DHCP in the firewall.  Could you edit the subnet mask in the pools to /32 so that the pools no longer match the IP interfaces (and thus will not function)?  Perhaps the cleanest option would be to copy those parts of the config to a file (whether in flash or on your PC).  "No" the pools to delete them.  When you're ready to restore DHCP service in the ADTRAN, just past that part of the config into the config prompt.  You don't need to reboot for that change.

           

          Best,

          Chris

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            • Re: Temporarily disable DHCP server without removing/altering pools?
              zprime New Member

              Yeah, the above is basically the route I'm going to take.  I have the fully-functioning config saved to a file both on the Netvanta and on my PC, and then I "no'd" the two pools and saved the config before packing up the router for shipment.

               

              When it gets to the site and after the T1s are tested, I can just paste back in the two pools, or I can restore the backup of the config to the startup-config and reboot.  I was just trying to see if there was any more "elegant" method to use.