splitting dhcp scope

Discussion in 'Server Networking' started by Joey, May 19, 2009.

  1. Joey

    Joey Guest

    we currently have a cluster which is servicing dhcp and wins.

    Is it possible to have 2 servers that I can split up the dhcp scope and
    still have redundancy if one server fails without using clustering?
     
    Joey, May 19, 2009
    #1
    1. Advertisements


  2. Yes, usually the 80/20 rule would apply. This would be a backup strategy if one of them were to go down. You can also opt for a 50/50 strategy, too for load balancing, but they cannot be combined between two different DHCP servers.

    80/20 RuleFor balancing DHCP server usage, use the 80/20 rule to divide scope addresses between DHCP servers. Figure 4.11 is an example of the 80/20 rule. ...
    http://technet.microsoft.com/en-us/library/cc958936.aspx

    Configuring scopes: Dynamic Host Configuration Protocol (DHCP)Jan 21, 2005 ... For balancing DHCP server usage, a good practice is to use the "80/20" rule to divide the scope addresses between the two DHCP servers. ....
    http://technet.microsoft.com/en-us/library/cc739076(WS.10).aspx

    --
    Ace

    This posting is provided "AS-IS" with no warranties or guarantees and
    confers no rights.

    Ace Fekay, MCSE 2003 & 2000, MCSA 2003 & 2000, MCSA Messaging, MCT
    Microsoft Certified Trainer


    For urgent issues, you may want to contact Microsoft PSS directly. Please
    check http://support.microsoft.com for regional support phone numbers.

    "Efficiency is doing things right; effectiveness is doing the right things." - Peter F. Drucker
    http://twitter.com/acefekay
     
    Ace Fekay [Microsoft Certified Trainer], May 19, 2009
    #2
    1. Advertisements

  3. Joey

    Joey Guest

    If I go with 80/20 rule. what happens if one for the dhcp server fails or go
    offline? what do I do with clients that cannot get IP address on the server
    that does not have a scope configured
    "Ace Fekay [Microsoft Certified Trainer]" <>
    wrote in message

    Yes, usually the 80/20 rule would apply. This would be a backup strategy if
    one of them were to go down. You can also opt for a 50/50 strategy, too for
    load balancing, but they cannot be combined between two different DHCP
    servers.

    80/20 RuleFor balancing DHCP server usage, use the 80/20 rule to divide
    scope addresses between DHCP servers. Figure 4.11 is an example of the 80/20
    rule. ...
    http://technet.microsoft.com/en-us/library/cc958936.aspx

    Configuring scopes: Dynamic Host Configuration Protocol (DHCP)Jan 21, 2005
    .... For balancing DHCP server usage, a good practice is to use the "80/20"
    rule to divide the scope addresses between the two DHCP servers. ...
    http://technet.microsoft.com/en-us/library/cc739076(WS.10).aspx

    --
    Ace

    This posting is provided "AS-IS" with no warranties or guarantees and
    confers no rights.

    Ace Fekay, MCSE 2003 & 2000, MCSA 2003 & 2000, MCSA Messaging, MCT
    Microsoft Certified Trainer


    For urgent issues, you may want to contact Microsoft PSS directly. Please
    check http://support.microsoft.com for regional support phone numbers.

    "Efficiency is doing things right; effectiveness is doing the right
    things." - Peter F. Drucker
    http://twitter.com/acefekay
     
    Joey, May 19, 2009
    #3

  4. The 80/20 rule means both servers have a scope configured, so I'm not sure what you mean? Check out the articles. The main server will have 80% of the scope, the other having 20%. If the main one goes down, the other will keep giving out addresses until you get the first one up.

    Or did you mean something else?

    Ace
     
    Ace Fekay [Microsoft Certified Trainer], May 19, 2009
    #4
  5. Why in the world did they ever dream up the 80/20 idea when the 50/50 is so
    much more logical?


    --
    Phillip Windell

    The views expressed, are my own and not those of my employer, or Microsoft,
    or anyone else associated with me, including my cats.
    -----------------------------------------------------


    "Ace Fekay [Microsoft Certified Trainer]" <>
    wrote in message

    The 80/20 rule means both servers have a scope configured, so I'm not sure
    what you mean? Check out the articles. The main server will have 80% of the
    scope, the other having 20%. If the main one goes down, the other will keep
    giving out addresses until you get the first one up.

    Or did you mean something else?

    Ace
     
    Phillip Windell, May 19, 2009
    #5
  6. Joey

    BillyBob Guest

    Just add both ip's of the DHCP servers, to your helper address on the router
    per subnet
     
    BillyBob, May 19, 2009
    #6
  7. Joey

    Joey Guest

    my thought you cannot have 2 dhcp servers on the same network. If I do have
    2 dhcp servers, any client on the network will get an ip from the first dhcp
    that responds? I still dont understand what 80/20 mean. from the diagram. I
    see the same scope configured on both servers but on different subnets.

    for our network, we only have one dhcp cluster servicing multiple vlans. I
    believe the router is doing some dhcp helper thing to help clients from
    different subnets find the dhcp cluster.


    "Ace Fekay [Microsoft Certified Trainer]" <>
    wrote in message

    The 80/20 rule means both servers have a scope configured, so I'm not sure
    what you mean? Check out the articles. The main server will have 80% of the
    scope, the other having 20%. If the main one goes down, the other will keep
    giving out addresses until you get the first one up.

    Or did you mean something else?

    Ace
     
    Joey, May 19, 2009
    #7
  8. Yes you can
    Yes that is correct.
    It is the same identical Scope except that Exclusions are use on each that
    limit what IP#s it can actually give out to Clients. I never do 80/20,..it
    doesn't make good sense to me,..I always do 50/50. One DHCP gives out the
    first half of the available addresses,...the second DHSP gives out the
    second half of the addresses (hence 50/50).

    --
    Phillip Windell

    The views expressed, are my own and not those of my employer, or Microsoft,
    or anyone else associated with me, including my cats.
    -----------------------------------------------------
     
    Phillip Windell, May 19, 2009
    #8

  9. The 80/20, or preferrably as Phillip mentioned, 50/50 idea has been around for quite some time. You can have two DHCP servers but as long as the IP ranges do not cross, you are good to go.

    Ace
     
    Ace Fekay [Microsoft Certified Trainer], May 19, 2009
    #9
  10. Ben M. Schorr - MVP (OneNote), May 19, 2009
    #10
  11. Hi Ben, good to hear from you!

    Ours doesn't quite have enough with only 50%,..but it would survive longer,
    giving me more time to fix the dead one than what I would have if I ran
    80/20 and it was the 80% one that died.
     
    Phillip Windell, May 19, 2009
    #11
  12. Once had a guy from MS tell me that they used to recommend 80/20 in the
    past,..but now recommend 50/50 and so it just depends on how old the
    material is you are reading. I don't know how accurate that is. It's hard
    for one tech guy at MS to speak for the whole company.


    --
    Phillip Windell

    The views expressed, are my own and not those of my employer, or Microsoft,
    or anyone else associated with me, including my cats.
    -----------------------------------------------------



    "Ace Fekay [Microsoft Certified Trainer]" <>
    wrote in message

    The 80/20, or preferrably as Phillip mentioned, 50/50 idea has been around
    for quite some time. You can have two DHCP servers but as long as the IP
    ranges do not cross, you are good to go.

    Ace
     
    Phillip Windell, May 19, 2009
    #12
  13. True. Just like originally the empty forest root domain and child domains was an original design recommendation, but that has changed. Originally the domain was a security boundary, but now many look at the forest as a security boundary based on the common Schema, EA, etc. I think another was originally to name the domain the same as the public namespace, but that has changed, too! It's all based on everyone's experience and feedback over the years. I like the 50/50 rule better.

    :)

    Ace
     
    Ace Fekay [Microsoft Certified Trainer], May 19, 2009
    #13
  14. Joey

    Joey Guest

    From the diagram the scopes are crossed. what do you mean by do not cross?

    Say I have a few scopes on one dhcp server

    10.10.10.0 - 10.10.11.254
    10.10.12.0- 10.10.13.254

    how do I split these up into 2 dhcp servers?


    "Ace Fekay [Microsoft Certified Trainer]" <>
    wrote in message

    The 80/20, or preferrably as Phillip mentioned, 50/50 idea has been around
    for quite some time. You can have two DHCP servers but as long as the IP
    ranges do not cross, you are good to go.

    Ace
     
    Joey, May 20, 2009
    #14
  15. Maybe overlap should have been the better word than 'crossed.'

    For 50/50:

    Server1:
    10.10.10.1 - 10.10.10.254
    10.10.12.1 - 10.10.12.254

    Server2:
    10.10.11.1 - 10.10.11.254
    10.10.13.1 - 10.10.13.254

    Ace
     
    Ace Fekay [Microsoft Certified Trainer], May 20, 2009
    #15
  16. Joey

    Joey Guest

    If I do it this way and server 1 fails. what happens if server2 doesnt have
    any available lease addresses on either one of the ranges?
    "Ace Fekay [Microsoft Certified Trainer]" <>
    wrote in message
    Maybe overlap should have been the better word than 'crossed.'

    For 50/50:

    Server1:
    10.10.10.1 - 10.10.10.254
    10.10.12.1 - 10.10.12.254

    Server2:
    10.10.11.1 - 10.10.11.254
    10.10.13.1 - 10.10.13.254

    Ace
     
    Joey, May 20, 2009
    #16
  17. If you have THAT many clients then you need to select larger ranges.

    --
    -Ben-
    Ben M. Schorr, MVP
    Roland Schorr & Tower
    http://www.rolandschorr.com
    http://www.officeforlawyers.com
    Author - The Lawyer's Guide to Microsoft Outlook 2007:
    http://tinyurl.com/5m3f5q



     
    Ben M. Schorr - MVP (OneNote), May 20, 2009
    #17
  18. Joey

    Bill Grant Guest

    Indeed. Each DHCP server must be capable of handling the complete load
    alone.

    With the 50/50 system, half of the available IP addresses are reserved on
    each DHCP server. If one server fails, removing the reservation allows all
    machines to use the one remaining server.

     
    Bill Grant, May 20, 2009
    #18
  19. I don't think there's any need to reserve the IP addresses. Just use
    distinct scopes on each server that are all in the same subnet.

    We have a client that uses a Class B scheme. They use 172.23.x.x.

    Their servers are 172.23.1.x
    Their workstations from one DHCP server are 172.23.2.x
    Their workstations from the other DHCP server are 172.23.22.x
    Remote workstations get 172.23.222.x
    They have network devices (like printers, etc.) on 172.23.3.x

    Either DHCP server can carry their entire network by itself, and there's
    no overlap. If either server goes down the other carries the network.
    And it's easy to tell which server a workstation got its address from
    (.2 or .22).

    It's simple, elegant, reliable and effective.

    --
    -Ben-
    Ben M. Schorr, MVP
    Roland Schorr & Tower
    http://www.rolandschorr.com
    http://www.officeforlawyers.com
    Author - The Lawyer's Guide to Microsoft Outlook 2007:
    http://tinyurl.com/5m3f5q



     
    Ben M. Schorr - MVP (OneNote), May 20, 2009
    #19
  20. Joey

    Joey Guest

    I have like 10 vlans

    it all goes like this

    10.10.1.0 - 10.10.2.254
    scope 10.10.1.50 - 10.10.2.254

    10.10.3.0 - 10.10.4.254
    scope 10.10.3.50 - 10.10.4.254

    10.10.5.0 - 10.10.6.254
    scope 10.10.5.50 - 10.10.6.254

    and so on

    how do I break this up into 2 dhcp servers? These 2 dhcp servers should be
    on the same broadcast domain right (vlan)?

     
    Joey, May 20, 2009
    #20
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.