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  • dhcp backup server

    I want to create a DHCP backup in case my main DHCP goes down. I know about 80/20 rule but what if I create two dhcp servers one with 10.100.5.0 and the other with the scope 10.100.14.0? Will this work? Any other suggestions?

  • #2
    Re: dhcp backup server

    How many devices in your scope?
    Screw the 80/20 rule and use the 50/50 rule.
    With your suggested IP ranges, what Subnet Mask were you intending on using?
    1 1 was a racehorse.
    2 2 was 1 2.
    1 1 1 1 race 1 day,
    2 2 1 1 2

    Comment


    • #3
      Re: dhcp backup server

      Thanks for the reply!!
      I am using super scopes becaue of the 10.0.0.0 addresses
      1st server:10.100.5.0 /24
      2nd server:10.100.14.0/24

      Comment


      • #4
        Re: dhcp backup server

        Unless you have a need for 2 different IP ranges then just change the Mask to /23, setup the 50/50 and you will have enough IPs to cover 500 devices.

        Do you really need to have the 2 different ranges? Remember the KISS rule.
        1 1 was a racehorse.
        2 2 was 1 2.
        1 1 1 1 race 1 day,
        2 2 1 1 2

        Comment


        • #5
          Re: dhcp backup server

          Hello,
          Backup servers need special technical specifications for replications.
          URL REMOVED BY MODERATOR
          Last edited by biggles77; 1st January 2010, 07:08. Reason: Member doesn't meet posting requirements

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          • #6
            Re: dhcp backup server

            Biggles77,
            If I use /23, how am I going to setup each DHCP server? Can you give me an example. I have a watchguard firewall with secondary networks 10.100.5.0 and 10.100.14.0 configured. Isn't there a limit. Ex. 10.100.5.1. to 10.100.5. 254? Can you link me to some examples. thanks for your reply.

            Comment


            • #7
              Re: dhcp backup server

              Originally posted by Biggles77
              How many devices in your scope?
              Originally posted by biggles77 View Post
              Unless you have a need for 2 different IP ranges then just change the Mask to /23, setup the 50/50 and you will have enough IPs to cover 500 devices.

              Do you really need to have the 2 different ranges? Remember the KISS rule.
              As per the above questions, answers are needed before other answers can be supplied. Main ones, why do you require 2 different IP ranges and how many devices do you need IPs for.

              I am guessing that you have one network/Domain that you want to have DHCP redundancy for, hence 2 DHCP Servers with a seperate IP range for each DHCP Server. BUT, i am only guessing. Tell us what you are wanting this for and what your network setup is like and we may be able to provide you with a better alternative.
              1 1 was a racehorse.
              2 2 was 1 2.
              1 1 1 1 race 1 day,
              2 2 1 1 2

              Comment


              • #8
                Re: dhcp backup server

                I have 300 devices. I configured two secondary networks from the the firewall to increase the necessary IP addresses. The two IP addresses are 10.100.5.0. and 10.100.14.0. Don't really need two subnets but need at least 300 ip addresses. thanks

                Comment


                • #9
                  Re: dhcp backup server

                  10.100.5.0/22 will give you 1022 usable IPs.
                  Create a Scope on DHCP Server 1 with IP Range 10.100.5.1 - 10.100.5.1022
                  Create an Exclusion for your Static IPs, Servers, Switches, Printers, WAPs and for the second part of the Range.
                  Exclusion 10.100.5.1 - 10.100.5.49 (for Static IPs) - example only
                  Exclusion 10.100.5.600 - 10.100.5.1022 (DHCP Server 2 Dynamic IPs)

                  DHCP Server 2
                  Range 10.100.5.1 - 10.100.5.1022
                  Exclusion 10.100.5.1 - 10.100.5.599 (DHCP Server 1 Dynamic IPs)

                  Make sure both DHCP Servers have the same:
                  003 Default Gateway
                  005 DNS
                  015 DNS Domain Name
                  044 WINS (if used)
                  046

                  This will give you 400+ Dynamic IPs available on both Servers and keep it all on the one Subnet.
                  If you need more IPs due to growth, change the Subnet Mask to 21 and change Exclusions to keep the available IPs availbe on each Server balanced.

                  Hope that all makes sense and it keeps it simple only having 1 Subnet.
                  Last edited by biggles77; 6th January 2010, 12:09.
                  1 1 was a racehorse.
                  2 2 was 1 2.
                  1 1 1 1 race 1 day,
                  2 2 1 1 2

                  Comment


                  • #10
                    Re: dhcp backup server

                    Thanks biggles77! As previouse stated, I thought you only use 1-256. I will give this a try.

                    Comment


                    • #11
                      Re: dhcp backup server

                      Originally posted by superhl View Post
                      Thanks biggles77! As previouse stated, I thought you only use 1-256. I will give this a try.
                      The highest decimal value on an IP octet is 255.
                      You could use 23 mask bits (Subnet mask 255.255.254.0)
                      That'll give you 510 hosts per subnet.
                      Caesar's cipher - 3

                      ZKHQ BRX HYHQWXDOOB GHFLSKHU WKLV BRX ZLOO UHDOLVH LW ZDV D ZDVWH RI WLPH!

                      SFX JNRS FC U6 MNGR

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                      • #12
                        Re: dhcp backup server

                        A4ndy, using /23 would not satisfy the redundancy need of 300 devices with 2 DHCP Servers (my description may have gotten a bit confusing). That is why I have suggested /22 or as I should have posted to make it clear to superhl 255.255.252.0

                        superhl you may wish to read some of the links listed below to fully learn and understand subnets and subnetting.
                        http://www.google.com.au/search?hl=e...&meta=&aq=f&oq=
                        1 1 was a racehorse.
                        2 2 was 1 2.
                        1 1 1 1 race 1 day,
                        2 2 1 1 2

                        Comment


                        • #13
                          Re: dhcp backup server

                          I am a little confused. I understand /22 will give 1022 addresses....This is what I don't unterstand, from a DHCP perspective, on the client side, the workstation cannot recieve a 10.100.5.300 address. That is why I am currently using 10.100.5.0-254 and 10.100.14.0-254. I hope I am being clear. Thanks

                          Comment


                          • #14
                            Re: dhcp backup server

                            Please Classless Inter Domain Routing. This will explain to you how it "joins" to C Class Subnets to make a contiguous range of IPs.

                            Also, read post #9 in this thread and notice that I have corrected a typo that was made in the IPs. The correction is in BOLD.

                            Basically the IP range goes from 10.100.5.1 to 10.100.8.254. Apologies for the typo as that did cause some confusion but please CIDR. If you look after networks, especially ones that grow, you need to understand subnetting. This is vital if you plan on doing any Cisco Certifications.
                            Last edited by biggles77; 11th January 2010, 06:17.
                            1 1 was a racehorse.
                            2 2 was 1 2.
                            1 1 1 1 race 1 day,
                            2 2 1 1 2

                            Comment


                            • #15
                              Re: dhcp backup server

                              Originally posted by biggles77 View Post
                              10.100.5.0/22 will give you 1022 usable IPs.
                              Create a Scope on DHCP Server 1 with IP Range 10.100.5.1 - 10.100.5.1022
                              Create an Exclusion for your Static IPs, Servers, Switches, Printers, WAPs and for the second part of the Range.
                              Exclusion 10.100.5.1 - 10.100.5.49 (for Static IPs) - example only
                              Exclusion 10.100.5.600 - 10.100.5.1022 (DHCP Server 2 Dynamic IPs)

                              DHCP Server 2
                              Range 10.100.5.1 - 10.100.5.1022
                              Exclusion 10.100.5.1 - 10.100.5.599 (DHCP Server 1 Dynamic IPs)

                              Make sure both DHCP Servers have the same:
                              003 Default Gateway
                              005 DNS
                              015 DNS Domain Name
                              044 WINS (if used)
                              046

                              This will give you 400+ Dynamic IPs available on both Servers and keep it all on the one Subnet.
                              If you need more IPs due to growth, change the Subnet Mask to 21 and change Exclusions to keep the available IPs availbe on each Server balanced.

                              Hope that all makes sense and it keeps it simple only having 1 Subnet.
                              10.100.5.0/22 will give you 1022 usable IPs.
                              Create a Scope on DHCP Server 1 with IP Range 10.100.5.1 - 10.100.8.254
                              Create an Exclusion for your Static IPs, Servers, Switches, Printers, WAPs and a second Exclusion for the second part of the Range on DHCP Server 2.
                              Exclusion 10.100.5.1 - 10.100.5.49 (for Static IPs) - example only
                              Exclusion 10.100.7.23 - 10.100.8.254 (DHCP Server 2 Dynamic IPs)

                              DHCP Server 2
                              Range 10.100.5.1 - 10.100.8.254
                              Exclusion 10.100.5.1 - 10.100.7.22 (DHCP Server 1 Dynamic IPs)

                              It is important that BOTH DHCP Servers have the same Subnet Mask of 255.255.252.0

                              Make sure both DHCP Servers have the same:
                              003 Default Gateway
                              005 DNS
                              015 DNS Domain Name
                              044 WINS (if used)
                              046

                              This will give you 400+ Dynamic IPs available on both DHCP Servers and keep all devices on the one Subnet.
                              If you need more IPs due to growth, change the Subnet Mask to 21 and change Exclusions to keep the available IPs availbe on each Server balanced.

                              Hope that all makes sense and it keeps it simple only having 1 Subnet.

                              I QUOTED post #9 here to make it easier to compare my initial mistakes to the corrections. For future reference, NEVER do subnetting if you haven't slept for 30+ hours (and no, I wasn't drunk ).
                              Last edited by biggles77; 11th January 2010, 06:59.
                              1 1 was a racehorse.
                              2 2 was 1 2.
                              1 1 1 1 race 1 day,
                              2 2 1 1 2

                              Comment

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