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

Posted: Thursday, February 26, 2009 12:50 AM by teamdhcp

Comments

DerekMorr said:

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?

# February 25, 2009 6:31 PM

Bink.nu said:

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

# February 27, 2009 9:50 AM

News said:

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

# March 1, 2009 3:12 PM

teamdhcp said:

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

# March 2, 2009 6:51 AM

BlogMS - Official Microsoft Team Blogs said:

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

# March 2, 2009 5:04 PM

Doug said:

>>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!

# April 29, 2009 1:46 PM

teamdhcp said:

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

Ajay

Team DHCP

# May 3, 2009 1:33 AM

Ashwin Kumar said:

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

# May 27, 2009 5:39 AM

teamdhcp said:

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

# May 27, 2009 5:48 AM

teamdhcp said:

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

# May 27, 2009 1:28 PM

Fei Yu said:

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?

# June 13, 2009 12:51 AM

teamdhcp said:

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

# June 15, 2009 5:28 AM

Richard Adams said:

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.

# June 25, 2009 10:45 AM

teamdhcp said:

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

# June 26, 2009 5:40 AM

Eric said:

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

# June 29, 2009 9:52 AM

teamdhcp said:

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

# June 29, 2009 11:10 PM

Ken P said:

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.

# January 4, 2010 7:32 AM

teamdhcp said:

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

# January 4, 2010 8:48 PM

Brougham Baker said:

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.

# January 20, 2010 7:58 AM

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What are the major changes?

Comments

DerekMorr said:

Bink.nu said:

News said:

teamdhcp said:

BlogMS - Official Microsoft Team Blogs said:

Doug said:

teamdhcp said:

Ashwin Kumar said:

teamdhcp said:

teamdhcp said:

Fei Yu said:

teamdhcp said:

Richard Adams said:

teamdhcp said:

Eric said:

teamdhcp said:

Ken P said:

teamdhcp said:

Brougham Baker said: