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Reservations in Split Scopes

  • Article

Split scopes are generally used to provide high-availability in a DHCP Server deployment, so that if one server goes down, another server is available from which clients continue to obain an IP address lease.

Lets take an example how Split scopes are created.We have the range from 10.0.0.1 to 10.0.0.200 and we want to configure the split scope in 50-50 manner then

1)-We will create the scope 10.0.0.1 to 10.0.0.200 on first server(say A), we will configure the Exclusion on server A from address 10.0.0.101 to 10.0.0.200 so that it serves the addresses from 10.0.0.1 to 10.0.0.100.

2)- We will create the scope 10.0.0.1 to 10.0.0.200 on second server(say B), we will configure the Exclusion on server B from address 10.0.0.1 to 10.0.0.100 so that it serves the adderss from 10.0.0.101 to 10.0.0.200.

Now some times we want that few network devices like Printers,fax m/c should always get constant IP address, this problem can be solved by two ways

1)-We can configure the same reservation on these boxes, this will make sure that these machine are getting reserved IP address only but it can be assigned by any of the server(A or B) 

2)- If we want that server A only should give IP X to client C and server B should not assign any address to that client then we can create the the reservation for client A on Server A and we can implement call out DLL on Server B that when ever this server receives the packet from client X, it should drop the packet. for more information for callout dlls one can refer https://blogs.msdn.com/anto_rocks/archive/2005/02/25/380510.aspx

 

Manu Jeewani

Windows Enterprise Networking

Comments

  • Anonymous
    January 01, 2003
    The comment has been removed

  • Anonymous
    January 01, 2003
    Now if only there were a way to manage clustering of DHCP servers, so you could implement this functionality without a custom extension to the DHCP service to deliberately break redundancy for static reservations. Oh wait, its been done!    draft-ietf-dhc-failover-12.txt

  • Anonymous
    January 01, 2003
    That is expected if you dont have exclusions. it is because if the client sends a "requested ip address" option and the server can provide that address , it will give that address. That is what is happening in your scenario. The DHCP server database is not is AD and there is no replication. Exclusion is required to provide better management of addresses being leased by 2 DHCP servers who have same scope.

  • Anonymous
    January 01, 2003
    The comment has been removed

  • Anonymous
    January 01, 2003
    we are looking into this. Thanks teamdhcp

  • Anonymous
    October 28, 2007
    That's nice split scopes but how can we prevent one of the server to fill up all the ip address ? If we do a 80-20 for example and all my clients register to the server that has 20% of the address and then the server with 80% of the address crash.... How could we force client to go through one machine unless that machine is down ? Through callout dll ?

  • Anonymous
    November 02, 2007
    The comment has been removed

  • Anonymous
    November 12, 2007
    Does Microsoft have any plan of implementing DHCP Failover or another sort of redundancy for DHCP? DHCP is quite critical.

  • Anonymous
    April 10, 2008
    Can I configure a reservation to a IP that is out of DHCP scope? Sorry for my bad english i´m from Brazil Thanks João

  • Anonymous
    September 07, 2009
    We configured two DHCP servers with split scope. We put all scopes under superscope without configuring the exclusion, from the test we did, we found that when one server is down the client registers it's ip on the second one, after restart. Can we assume that that both DHCP servers shares the same DB which stored in the Active Directory? If so, what is the purpose of excluding the negative range on any other server?

  • Anonymous
    March 07, 2010
    Hi, Is there any solution to this yet? We stopped our migration just to get this fixed. Best regards, Rene