Microsoft Windows DHCP Team Blog

DHCP Server Callout API usage

2009-07-06T09:03:00Z

Microsoft DHCP Server Callout API provides a way for developers to access the critical phases of DHCP protocol processing in Windows Server 2003 family and later. This enables developers to: · Create customized extensions to the Microsoft DHCP Server · Monitor statistics · Create parallel lease databases · Provide other customized solutions var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js'...(read more)

Rogue DHCP Server detection

2009-07-03T09:58:00Z

Overview Rogue DHCP servers are those DHCP servers that are misconfigured or unauthorized unknowingly or those that are configured with a malicious intent for network attacks. Either be the case the impact on clients that are serviced by the rogue DHCP servers are critical. That is the clients would experience network access problems due to rogue DHCP server leasing incorrect IP addresses & incorrect options to the client. Security threats are caused when malicious user with rogue DHCP server...(read more)

DHCP Server Performance in Windows Server 2008 R2

2009-06-29T13:45:00Z

This blog post details the performance improvement of DHCP Server in Windows Server 2008 R2 over prior releases. The results published are from a lab environment....(read more)

Option based IP Address assignment Callout Dll

2009-06-12T12:40:00Z

Overview DHCP administrators would like to manage address assignment in the network, by assigning IP address to DHCP clients based on vendor/user class identifier from distinct address ranges in the subnet. This functionality can be added to the Microsoft DHCP Server, by installing DHCP Server Option Based IP Address Assignment Callout package. This callout dll allows the administrators to define rules for assigning IP addresses from specific IP address ranges based on the vendor/ user classes of...(read more)

Windows 7 RC is available for TechNet and MSDN subscribers to download

2009-05-01T11:03:00Z

We are pleased to announce that the Windows 7 Release Candidate (RC) is available for immediate download to our TechNet and MSDN subscribers. If you’re not a TechNet Plus subscriber, please click here to learn about the benefits of becoming one. Windows 7 RC will be made available to the general public on May 5, 2009. You will then be able to download Windows 7 RC here , through the Springboard Series on TechNet. Windows 7 Ultimate is the Release Candidate edition; it will be available in 32-bit...(read more)

DHCPv6 Information-Refresh Time Option

2009-04-20T11:06:00Z

DHCPv6 Stateless Clients obtain configuration data from DHCP Server, by sending Information-request messages. The configuration data typically has no associated lifetime, hence there is no information telling a host when to refresh its configuration information. DHCPv6 Information-Refresh time option (Option 32), specified in RFC-4242 allows stateless clients to refresh configuration data periodically. The information refresh time specifies an upper bound for how long a client should wait, before...(read more)

DHCPv6 User Class Option

2009-04-20T11:03:00Z

RFC3315 specifies User Class Option for IPv6 hosts. DHCP administrators may define specific user class identifiers to convey information about a client's software configuration or about its user's preferences. User classes are created to support the implementation of various scenarios like: To identify various clients in specific site and location. For example the computers and printers on the same floor can be configured with the same user class. Assign specific options based on the client’s user...(read more)

DHCP Server Events Tool

2009-03-20T15:24:00Z

This tool can be used by DHCP Administrators to view all the events generated by DHCP Server directly in MMC. This tool can also be very handy in managing the MAC Based Filtering where you can see the list of people entering your network and you will be able to remotely add them to Allow/Deny list without affecting the Service. You can also see the scope change/ Activity Logs and System Events in this MMC. This tool is a MMC Snap-In and can be used to view the events from a Remote Server similar...(read more)

DHCPv6 - Understanding of address configuration in automatic mode and installation of DHCPv6 Server

2009-03-03T12:58:00Z

Understanding of address configuration in automatic mode Windows Server 2008 and Windows Vista include a DHCPv6-capable DHCP client that will perform stateful address autoconfiguration with a DHCPv6 server. Windows Server 2008 includes a DHCPv6-capable DHCP server. A host (DHCP Client) can configure itself with an IPv6 address to be used on the network. Address configuration can be performed in a stateful or a stateless mode. A host can use both stateless and stateful address configuration completely...(read more)

How to monitor and audit DHCP Server configuration changes for compliance

2009-03-03T12:46:00Z

DHCP Server of Windows Server 2008 R2, supports DHCP activity logging, that is it allows DHCP Administrators to monitor the configuration changes of the DHCP Servers. Therefore the events pertaining to DHCP activity logging, will be logged with additional information like: Date and time of event occurrence, IP Address and host name of the DHCP Server on which the event occurred and user name of the administrator who made the change. These events can be seen in the following location in eventviewer:...(read more)

DHCP Server service security enhancement

2009-03-03T12:41:00Z

DHCP Server service is moved under Network Service account from what it used to be a Local System account untill Windows Server 2008. 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. var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript...(read more)

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

2009-02-25T22:50:00Z

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...(read more)

Migration of DHCP Server from Windows Server 2003 to Windows Server 2008

2009-02-18T14:34:00Z

Microsoft product support team often encounters migrated DHCP servers which are dysfunctional. The reason quite often for the bad state of the DHCP server is because backup/restore has been used by the customers for migrating the DHCP server across server versions (e.g. migrating from Windows Server 2003 DHCP to Windows Server 2008). Backup and Restore are not expected to work across server versions as the DHCP database format has changed between Windows Server 2003 and Windows Server 2008. The recommended...(read more)

MAC Filter Import Tool

2009-02-16T16:54:00Z

Hello Everybody, Thanks for all those who tried the MacFilterCallout dll . As you all must have checked out by now that Link Layer Filtering feature is a part of Windows Server 2008 R2 DHCP Server. DHCP Server team has come up with a GUI based tool which will let an administrator import the MAC addresses specified in MACList.txt file (used by MacFilterCallout dll), into the allow/deny list of Windows Server 2008 R2 DHCP Server. This tool will work only on Windows Server 2008 R2 or above. DHCP Server...(read more)

DHCP Broadcast flag handling in Windows 7

2009-02-12T19:44:00Z

1. DHCP Broadcast flag: DHCP messages have ‘flags’ field. The first bit in this field indicates whether the client is expecting a broadcast or unicast response from the DHCP server \ Relay agent. When the bit is set to 1, it indicates that the client expects broadcast response, and when the bit is set to 0, it indicates that the client expects a unicast response. While the majority of the DHCP Servers and Relay Agents support both the values for the broadcast flag, there are still few of them which...(read more)