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Using Server 2012ís DHCP only, how to add IP addresses to support 300 Pcís

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  • Using Server 2012ís DHCP only, how to add IP addresses to support 300 Pcís

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ID:	494798 ​Iím a volunteer for a school that uses Server 2012 and its DHCP function. All DHCP is handled via the server. We are currently close to exceeding the 253? limit. Iím not real technical regarding server and network, so bear with me. When I converted from Server 2003 last year, I used the same DHCP parameters because we were not exceeding the limit. We now expect to get additional iPads and/or netbooks that will take us over the limit.
    Iím probably not using the correct terminology, but the subnet mask is 255.255.255.0 and the Cisco router is 192.168.0.1.
    How do I configure DHCP to allow for another 200+ addresses without causing other issues to our environment?

  • #2
    Your terminology is correct, by the way


    You need to expand your entire subnet. This will require changes on all devices, including routers and switches. It's easier than messing around with multiple subnets and routing though, or playing with CIDR.

    You currently have:
    Network Address: 192.168.0.0/24 - this is a Class C subnet and gives you 254 useable addresses.
    Subnet mask: 255.255.255.0 (/24)
    Broadcast: 192.168.0.255
    Min host: 192.168.0.1
    Max host: 192.168.0.254

    What you need is:
    Network address: 192.168.0.0/23 (Class B subnet, 510 usesable)
    Subnet mask: 255.255.254.0 (/23)
    Broadcast: 192.168.1.255
    Min host: 192.168.0.1
    Max host: 192.168.1.254

    some links to help:

    www.subnet-calculator.com
    www.jodies.de/ipcalc


    Basically, reconfigure all your staticlly addressed devices and give them 255.255.254.0 subnet masks
    Then delete your dhcp scope and create a new one.
    Please do show your appreciation to those who assist you by leaving Rep Point https://www.petri.com/forums/core/im.../icon_beer.gif

    Comment


    • #3
      Andy, don't forget to mention to the OP that they will also need to change the Subnet Mask on any devices that have a Static IP.

      gmklabisch, would also suggest, if not already implemented, to use DHCP Reservations for your Network Printers. Saves having to make visits to each device to change the Mask. Make a document with all of the MAC address so you don't need to type them when creating or changing the Reservation.
      1 1 was a racehorse.
      2 2 was 1 2.
      1 1 1 1 race 1 day,
      2 2 1 1 2

      Comment


      • #4
        Welcome back, Chris
        Tom Jones
        MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
        PhD, MSc, FIAP, MIITT
        IT Trainer / Consultant
        Ossian Ltd
        Scotland

        ** Remember to give credit where credit is due and leave reputation points where appropriate **

        Comment


        • #5
          Thanks you both for your informative replies. I'm going to try to implement this weekend. I have a few questions before though:
          1. I've tested using the powershell to add a reservation in my current environment. e.g. Import-Csv Reservations.csv | Add-DhcpServerv4Reservation Any issues using this when I implement over the weekend?
          2. After I delete the old Scope and add the new, should the new Scope Name still be 192.168.0.0?
          3. Per your suggestion, I'm planning on reserving all my network printers. Will I have to power these off & on, or will the changes take place immediately & automatically?
          4. I'm also planning on reserving my switches & other routers (none of these have DHCP enabled and act as Access Points only). Is this feasible and if so will I have to power these off & on, or will the changes take place immediately & automatically?
          5. I'll be using the New Scope wizard. I'm assuming on the IP Address Range screen I will use 192.168.0.1 for the Start IP address & 192.168.1.254 for the End IP address. I will change the length from 24 to 23 and use the Subnet Mask 255.255.254.0. I believe this is correct, but would like you to comment.

          Thanks in advance for your help, it is truly appreciated. And Merry Christmas!!

          Comment


          • #6
            Hi guys!.. I was successful in implementing today. Thanks for all your help!!

            Comment


            • #7
              I found a new problem. When I tested initially, I tested to make sure that printers in one subnet (192.168.0.xxx) could be accessed by a PC in the other. However, what I'm now finding out is that any PC in the "upper" subnet (192.168.1.xxx) cannot access the internet. I have no proxy servers. I get a timeout error trying to access a website. Any ideas?

              Comment


              • #8
                Can you post an IPCONFIG /ALL from a "good" PC and a "problem" one
                Tom Jones
                MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
                PhD, MSc, FIAP, MIITT
                IT Trainer / Consultant
                Ossian Ltd
                Scotland

                ** Remember to give credit where credit is due and leave reputation points where appropriate **

                Comment


                • #9
                  Hopefully,I'm attaching 2 Word docs as requested. Also, I connect to the school from home via VPN and I can't RDP into the "bad" one either, IPCONFIG from PC not able to access Internet.doc IPCONFIG from PC that is able to access Internet.doc

                  Comment


                  • #10
                    Sorry, but I will NOT open a potential security risk
                    Please use plain text or (better still) just paste into your reply
                    Tom Jones
                    MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
                    PhD, MSc, FIAP, MIITT
                    IT Trainer / Consultant
                    Ossian Ltd
                    Scotland

                    ** Remember to give credit where credit is due and leave reputation points where appropriate **

                    Comment


                    • #11
                      Sorry, here they are. Thanks for helping me out!
                      This one did not work. It's in the 192.168.1 subnet. I can RDP it from the local server, but not from VPN.


                      Windows IP Configuration

                      Host Name . . . . . . . . . . . . : SJSNETBOOK-03
                      Primary Dns Suffix . . . . . . . : xxxxx.local
                      Node Type . . . . . . . . . . . . : Hybrid
                      IP Routing Enabled. . . . . . . . : No
                      WINS Proxy Enabled. . . . . . . . : No
                      DNS Suffix Search List. . . . . . : xxxxx.local

                      Wireless LAN adapter Wireless Network Connection:

                      Connection-specific DNS Suffix . : xxxxx.local
                      Description . . . . . . . . . . . : Broadcom 802.11n Network Adapter
                      Physical Address. . . . . . . . . : E0-06-E6-2A-83-2C
                      DHCP Enabled. . . . . . . . . . . : Yes
                      Autoconfiguration Enabled . . . . : Yes
                      Link-local IPv6 Address . . . . . : fe80::b52c:ebfd:4818:9478%12(Preferred)
                      IPv4 Address. . . . . . . . . . . : 192.168.1.20(Preferred)
                      Subnet Mask . . . . . . . . . . . : 255.255.254.0
                      Lease Obtained. . . . . . . . . . : Thursday, January 07, 2016 9:51:14 AM
                      Lease Expires . . . . . . . . . . : Thursday, January 07, 2016 1:51:14 PM
                      Default Gateway . . . . . . . . . : 192.168.0.1
                      DHCP Server . . . . . . . . . . . : 192.168.0.67
                      DHCPv6 IAID . . . . . . . . . . . : 333448934
                      DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-19-54-FE-05-B8-88-E3-03-7A-B7
                      DNS Servers . . . . . . . . . . . : 192.168.0.67 4.2.2.1 192.168.0.67
                      Primary WINS Server . . . . . . . : 192.168.0.67
                      NetBIOS over Tcpip. . . . . . . . : Enabled

                      Ethernet adapter Local Area Connection:

                      Media State . . . . . . . . . . . : Media disconnected
                      Connection-specific DNS Suffix . : xxxxx.local
                      Description . . . . . . . . . . . : Atheros AR8152/8158 PCI-E Fast Ethernet Controller (NDIS 6.20)
                      Physical Address. . . . . . . . . : B8-88-E3-03-7A-B7
                      DHCP Enabled. . . . . . . . . . . : Yes
                      Autoconfiguration Enabled . . . . : Yes
                      Tunnel adapter isatap.xxxxx.local:
                      Media State . . . . . . . . . . . : Media disconnected
                      Connection-specific DNS Suffix . : xxxxx.local
                      Description . . . . . . . . . . . : Microsoft ISATAP Adapter
                      Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
                      DHCP Enabled. . . . . . . . . . . : No
                      Autoconfiguration Enabled . . . . : Yes
                      Tunnel adapter Teredo Tunneling Pseudo-Interface:
                      Media State . . . . . . . . . . . : Media disconnected
                      Connection-specific DNS Suffix . :
                      Description . . . . . . . . . . . : Teredo Tunneling Pseudo-Interface
                      Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
                      DHCP Enabled. . . . . . . . . . . : No
                      Autoconfiguration Enabled . . . . : Yes

                      Tunnel adapter isatap.{A9192919-8656-4849-999B-3489317FBABC}:

                      Media State . . . . . . . . . . . : Media disconnected
                      Connection-specific DNS Suffix . :
                      Description . . . . . . . . . . . : Microsoft ISATAP Adapter #2
                      Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
                      DHCP Enabled. . . . . . . . . . . : No
                      Autoconfiguration Enabled . . . . : Yes

                      This one works fine.

                      Microsoft Windows [Version 10.0.10586]
                      (c) 2015 Microsoft Corporation. All rights reserved.

                      C:\Users\administrator>ipconfig /all

                      Windows IP Configuration

                      Host Name . . . . . . . . . . . . : COMPUTERLAB4W10
                      Primary Dns Suffix . . . . . . . : xxxxx.local
                      Node Type . . . . . . . . . . . . : Hybrid
                      IP Routing Enabled. . . . . . . . : No
                      WINS Proxy Enabled. . . . . . . . : No
                      DNS Suffix Search List. . . . . . : xxxxx.local

                      Ethernet adapter Local Area Connection:

                      Connection-specific DNS Suffix . : xxxxx.local
                      Description . . . . . . . . . . . : Broadcom NetXtreme Gigabit Ethernet
                      Physical Address. . . . . . . . . : 00-1F-29-DD-1B-C6
                      DHCP Enabled. . . . . . . . . . . : Yes
                      Autoconfiguration Enabled . . . . : Yes
                      Link-local IPv6 Address . . . . . : fe80::35be:4087:8aa:2a33%2(Preferred)
                      IPv4 Address. . . . . . . . . . . : 192.168.0.26(Preferred)
                      Subnet Mask . . . . . . . . . . . : 255.255.254.0
                      Lease Obtained. . . . . . . . . . : Tuesday, January 05, 2016 3:14:27 PM
                      Lease Expires . . . . . . . . . . : Saturday, January 09, 2016 3:14:29 PM
                      Default Gateway . . . . . . . . . : 192.168.0.1
                      DHCP Server . . . . . . . . . . . : 192.168.0.67
                      DHCPv6 IAID . . . . . . . . . . . : 234889001
                      DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-19-19-CA-A0-00-1F-29-DD-1B-C6
                      DNS Servers . . . . . . . . . . . : 192.168.0.67
                      4.2.2.1
                      192.168.0.67
                      Primary WINS Server . . . . . . . : 192.168.0.67
                      NetBIOS over Tcpip. . . . . . . . : Enabled

                      Tunnel adapter isatap.xxxxx.local:

                      Media State . . . . . . . . . . . : Media disconnected
                      Connection-specific DNS Suffix . : xxxxx.local
                      Description . . . . . . . . . . . : Microsoft ISATAP Adapter
                      Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
                      DHCP Enabled. . . . . . . . . . . : No
                      Autoconfiguration Enabled . . . . : Yes

                      C:\Users\administrator>

                      Comment


                      • #12
                        Have you changed the subnet mask on the router to 255.255.254.0 ?
                        Tom Jones
                        MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
                        PhD, MSc, FIAP, MIITT
                        IT Trainer / Consultant
                        Ossian Ltd
                        Scotland

                        ** Remember to give credit where credit is due and leave reputation points where appropriate **

                        Comment


                        • #13
                          No, but I just did and the PC can now access the Internet. Thanks much for your help in solving this!! One last issue, I still can't RDP to it via VPN. Is there some other change I need to make that you are aware of? I use Cisco VPN client on a Cisco ASA5505 router.

                          Comment


                          • #14
                            Originally posted by gmklabisch View Post
                            No, but I just did and the PC can now access the Internet. Thanks much for your help in solving this!! One last issue, I still can't RDP to it via VPN. Is there some other change I need to make that you are aware of? I use Cisco VPN client on a Cisco ASA5505 router.
                            you'll probably need to change your routemapping for your VPN as well
                            it will have no concept of 192.168.1.0/16
                            Please do show your appreciation to those who assist you by leaving Rep Point https://www.petri.com/forums/core/im.../icon_beer.gif

                            Comment


                            • #15
                              Any suggestions on how to change routemapping for my VPN ? I'm not really sure how.

                              Comment

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