New features in DHCP for Windows Server 2008 R2 / Windows 7


What are the major changes?

The DHCP server in Windows Server 2008 R2 has invested in the areas of security, reliability, manageability and usability. Similarly on the DHCP Client in Windows 7 has invested on certain optimization for obtaining IP Address.

 

The following changes are available in DHCP server in Windows Server 2008 R2:

 

·         Supports MAC address based network access control mechanism, with the Link Layer based Filtering feature. With this feature DHCP Administrator can control issuance/denial of DHCP leases/IP addresses.

 

·         Supports prevention of name squatting issues caused due to non-Windows OS machines, with the Name Protection feature. Using this feature one could prevent registration of non-Windows OS machine with a same name that is already registered for another machine in DNS Server.

 

·         Supports prevention of exhaustion of IP addresses at scope level especially for the deployments catering to redundancy/high-availability scenarios like Split-Scope. This feature is available only for IPv4 network and not for IPv6 network as in case of latter exhaustion of addresses is not an issue.

 

·         Supports DHCP activity logging, allows DHCP Administrators to monitor the configuration changes of the DHCP Servers. DHCP Administrators would use this feature for network security / IT compliance auditing purposes.

 

·         Supports migration of DHCP Server role using Windows Server Migration Tool (WSMT).

 

·         DHCP Server service is moved under Network Service account from Local Service account. With this the DHCP Server service that runs in the context of the Network Service account presents the computer’s credentials to remote servers. Also the advantage with Network Service is it has very few privileges and can do less damage on the server if compromised.

 

·         Usability and operability enhancements of DHCP Server like:

          Auto-population of certain network interface fields like DNS Server addresses (both IPv4 and IPv6), WINS Server addresses, during installation and configuration of scope.

          Interpretive Icons for better readability.

          Wizard based split-scope configuration for ease and error free split-scope deployment.

          Address leases to filter (multiple select supported) for ease of Link Layer based filter configuration for leased clients.

          Address leases to reservation (multiple select supported) for ease of reservation configuration for leased clients.

          In the product scenario/task based help content for Windows Server 2008 R2 features.

 

·         Supports DHCPv6 Option 15 (User Class). This is used by client to identify the type or category of user or application it represents. It involves both DHCP Server and Client side implementation.

 

·         Support of DHCPv6 Option 32 (Information Refresh Time). This specifies an upper bound for how long a client should wait before refreshing information retrieved from DHCPv6. It involves both DHCP Server and Client side implementation.

 

·         Better performance and scalability achieved through lease database caching. Read more about it here.

 

 

The DHCP client of Windows 7 has support for optimization to obtain IP Address using SSID caching.

 

·         Supports SSID caching so that, laptop devices with Windows 7 could get IP Address in a lesser time in a Wireless LAN network during revisits to the same.

 

·         Extended NDF and unified tracing to support additional scenario.

 

·         Broadcast bit flag behaviour is updated to toggle between ‘0’ and ‘1’ and also would cache the last successful broadcast bit setting for which the client received IP Address. This way it would ensure the client to acquire the address properly, irrespective of the support for the flag by the 3rd party DHCP Server Relay Agent.

 

·         Support of DHCPv6 Option 32 (Information Refresh Time). This specifies an upper bound for how long a client should wait before refreshing information retrieved from DHCPv6.

 

 

 Team DHCP


Comments (36)

  1. Anonymous says:

    The DHCP server in Windows Server 2008 R2 has invested in the areas of security, reliability, manageability

  2. Anonymous says:

    Thanks Imran! It will  be great if you could share feedback on any product functionality missing in Windows DHCP server which is the reason for the current deployment in your organization.

  3. Anonymous says:

    By proxy server, do you mean DHCP relay agent. If so, the proxy server (relay) needs to be configured with IP address of the DHCP server and not the other way around.

  4. Anonymous says:

    214 Microsoft Team blogs searched, 101 blogs have new articles in the past 7 days. 237 new articles found

  5. Anonymous says:

    Windows Server 08 R2 has Clustering and 80:20 (with secondary server delay)support for Higher availability .

  6. Anonymous says:

    In Dhcpv4 u can configure a delay on the scope which you want to give lesser preference. You can get more information here http://blogs.technet.com/teamdhcp/archive/2009/01/22/how-to-prevent-address-exhaustion-from-secondary-server-in-split-scope-deployment.aspx

    -Tushar

  7. Anonymous says:

    Windows Server 2008 as well as Windows Server 2008 R2 support option 121 classless static routes. This can configured as a server or scope option. Is that what you were looking for.

    Prasad

  8. Anonymous says:

    hi Richard,

    DHCP in 2008R2 won’t be controllable from powershell. Please let us know what are the queries/control that you think will be simple if implemented using powershell but difficult to implement currently.

    Please send the mail at dhcpblog AT microsoft DOT com

    Thanks

    Ranu

  9. Anonymous says:

    Imran, hope that you had a chance to review the new functionality in Windows Server 2012 i.e. DHCP Failover, DHCP policies, DHCP PowerShell cmdlets and IPAM.

  10. Anonymous says:

    In DHCPv6, there is provision at the protocol level for a server preference field which is supported by Windows DHCP server. For DHCPv4 however, there is no such provision at the protocol level. Configuring delay at the scope level would be the way to go.

    Prasad

  11. Anonymous says:

    You mention that you don’t have IP address exhaustion protection for IPv6. Does this mean that a client can request an unlimited number of IA_NA leases? If that’s the case, isn’t this a potential DOS attack, since the server has to maintain state for each lease?

  12. Anonymous says:

    I'm also curious about RickC's question. Any known issues when using netsh to import into 2K8 R2? We currently have two 2008 DHCP servers and we are looking to migrate over to R2.

    Also what is Microsoft's stance on managing the R2 servers from older support tools such as the 2K3 admin pack?

  13. Anonymous says:

    I applied the hotfix and now I’m having a different problem after applying last month patches. the DHCP servers are loosing the router setting and changing the lease renew from 30 to 0 days. I have several scopes with the same problem. I experience the same problem in two servers. I don’t which patch is causing the problem.

  14. Anonymous says:

    It is not possible to specify Ipv6 scope prefix length other than 64 in Win2k8 R2. Can you please provide more information regarding why this is needed.

  15. Anonymous says:

    I am not sure about the post, but AFAIK you can implement a callout dll which would delay your offer by 5 secs. You register this callout dll on secondary server.

    You can get a lot of material about writing callout dlls for MS dhcp server, one of which is http://msdn.microsoft.com/en-us/library/aa363389(VS.85).aspx

    Thanks,

    Subhash Badri

  16. Anonymous says:

    I have recently migrated my company from (2) Windows 2003 DHCP servers to (2) Windows 2008 R2 DHCP servers, approximately 80 scopes.  The issue that I’m seeing is some of my printers that are DHCP are now showing up in the scopes with a reservation.  It reads like this:

    Client IP    Name         Lease Expiration

    10.0.136.51  10.0.136.51  Reservation (inactive)

    Type          Unique ID

    DHCP/BOOTP    00204a8v585c

    These clients never had a reservation before but now they do.  I’m worried that DNS will not get updated correctly now and cause some issues with my print servers.  Also, the scopes are set to DHCP only but the clients show up as DHCP/BOOTP for the client type.  Please advise

    Thank you

    Brian

  17. Anonymous says:

    You can convert your active leases into reservations, starting with Windows Server 2008 R2.

    Ajay

    Team DHCP

  18. Anonymous says:

    The DHCP server in Windows Server 2008 R2 has invested in the areas of security, reliability, manageability

  19. Anonymous says:

    Hi Josh,

    For setting up reservations, the reservedIP needs to be in the address range configured for the scope. Allowing of creation of reservations outside the range was causing some undesirable behavior – scope configuration getting wiped out. Hence, this change was done in Windows Server 2008 R2.

    However, a reservation can be in the exclusion range of the scope as a reservation gets preference over exclusion.

    Thanks,

    Prasad

    Team DHCP

  20. Anonymous says:

    Hi Ken,

    Thanks for your feedback. If I understood your request correctly, you are looking for a dialogue which allows for providing a name and description to the reservation while converting a lease to a reservation. Is that correct.

    Prasad

    Team DHCP

  21. Anonymous says:

    I have a problem with reservations in Windows 2008 r2. If I have more than one reservation the reservation is lost after one day or more when I have two Windows 2008 r2 DHCP servers in the network. Using only one windows 2008 r2 dhcp server works fine. The problem arises when the second dhcp server enters the network.

    Right now I am using two Windows 2008 servers and then everything works as per design. I have reinstalled the w2k8r2 servers several times, I have tried using the bootp setting, the dhcp setting and the setting named both.

    When I am setting it up I am using best practices 80/20 with exclusions for the addresses that belong to the other dhcp server.

    I have been using Windows 2008 dhcp for two years and never had a problem with this setup. Can you tell my why I am having this problem with windows 2008 r2 dhcp?

  22. Anonymous says:

    Hi Mikael,

    Look at the blog post at: http://blogs.technet.com/teamdhcp/archive/2010/04/19/dhcp-server-deletes-reservations.aspx

    Thanks,

    Prasad

    Team DHCP

  23. Doug says:

    >>Address leases to reservation (multiple select supported) for ease of reservation configuration for leased clients.

    We have been wanting this for years!!!!! There is no reason I shouldn’t be able to right-click a lease and convert it to a reservation!

  24. Ashwin Kumar says:

    Hi,

    I know this query is way off topic but was wondering if there is a posssibility to give preference to a particular DHCP server [maybe using Server IP in the DHCP Offer]? This is purely for use in a lab environment? Any suggestions would be greatly helpful!

    –Ashwin

  25. Fei Yu says:

    Hi there,

    Are there any options to use Windows Server 2008 to issue classless static routes?

    This feature is available in Windows Server 2003 DHCPs

    I dun see that its configurable in WIndows Server 2008… please advice any workaround in R2?

  26. Richard Adams says:

    Will DHCP in 2008R2 be FULLY controllable from Powershell? In all previous versions there has not even been so much as a MOF to allow queries/control via WMI.

  27. Eric says:

    Hi,

    I’ve read a post some time ago that contained VB code to compile a DLL that should be registerred on the Windows 2003 DHCP server of which you want to delay the DHCP offer by for example 5 seconds.

    Do you know about this article? It’s something I want to implement at this moment because we don’t have the opportunity to implement 2008R2 at this moment (yet) but still require a stand-by DHCP server that should respond a few seconds after the primary server.

    I hope you know about this.

    Thanks,

    Eric

  28. Ken P says:

    I echo a comment earlier about waiting for years for the ability to convert a lease into a reservation. Unfortunately, I rarely use the leased IP address when making a reservation. A huge step forward, just stopped short of perfect. Please add the reservation edit form before the reservation is saved.

  29. Brougham Baker says:

    Yes please Prasad! I do the same as Ken and the ability to change the ip address of a lease when making a reservation would be very useful especially now that a lot of the old tricks from 2003 don’t work anymore.

    I would plug a device in, find the lease. From I would copy the name  and save the reservation with a blank mac, then copy the mac to the new reservation on the address I wanted. Delete the lease and reboot. Job done!

    Now I get name already exists or mac already exists or I can’t save it with an invalid mac.

  30. Josh Taylor says:

    I have implemented Windows 2008 R2 DHCP into my network and Im having one issue. Are you no longer able to set up reservations for addresses that are not in your scope on the server? Before R2 it seemed that as long as the address was in the same subnet I was ok but now it looks like I cant a reservation for an address unless it is available in the scope.

    Thanks,

  31. Joel Gallay says:

    Is there a way to add this ability to Filter DHCP, Allows & Denys to Windows Server 2008 without going to R2?

  32. WD says:

    Is it still advisable to use best practices 80/20 if you have 2 DHCP servers running Win2008 R2 in the network? or there is a better way for load sharing and failover.

    Thanks

  33. RickC says:

    Your team blog shows DHCP migration from 2003 servers to 2008 server using netsh commands.  Does this also apply to 2008 R2?  Is there any problem moving from 2003 R2 32bit to 2008 R2?

  34. AB says:

    What about IPv6 scope prefixes? In Dibbler (open source DHCPv6) you can define prefixes that are longer than /64. In Windows 2008 you can't. Is it possible to define your own masks, being longer than /64 for subnets in R2?

  35. Eric says:

    I have Win 2008 server as DHCP and is connected via router. The router is the default gateway to the internet. How can I point the DHCP server to use the proxy server automatically. Im using Fedora/linux as my proxy server…

    need help

    Thanks

  36. Imran says:

    DHCP in Server 2008 R2 has best performance, But most of the organisation used dhcp in router.