INFO: Configuring Windows CE to Send and Receive DHCP Options (290279)
The information in this article applies to:
- Microsoft Windows CE Operating System, Versions 3.0
- Microsoft Windows CE Operating System, Versions 2.12
- Microsoft Windows CE Operating System, Versions 2.11
- Microsoft Windows CE Operating System, Versions 2.0
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256986 Description of the Microsoft Windows Registry
SUMMARY
Dynamic Host Control Protocol (DHCP), as specified in RFC 2131, is implemented in Windows CE beginning with version 2.0. The main purpose of DHCP is to enable dynamic configuration of network addressing parameters. However, it also includes provisions for requesting other information from the server (see RFC 1533). This article describes the mechanism used by Windows CE to request additional DHCP options and retrieve information returned by the server.
MORE INFORMATION
There are two categories of option support in DHCP: requested options, which are used to obtain additional information from the server, and send options, which are used to give additional information to the server. Refer to RFC 1533 for a full list of DHCP-defined options.
Requested Options
The default list of options requested from the server includes the following: | Subnet mask (1) | Specifies the subnet mask to use | | Router (3) | Specifies the list of IP addresses for routers on the client's subnet | | Domain name server (6) | Specifies a list of IP addresses for DNSs on the network | | Domain name (15) | Specifies the DNS domain name that the client should use for DNS host name resolution | | NetBIOS over TCP/IP name server (44) | Specifies a list of IP addresses for NetBIOS name servers (NBNS) | | NetBIOS over TCP/IP node type option (46) | Allows configurable NetBIOS over TCP/IP clients to be configured as described in RFC 1001/1002, where 1=b-node, 2=p-node, 4=m-node, and 8=h-node | | NetBIOS over TCP/IP scope (47) | Specifies a string that is the NetBIOS over TCP/IP scope ID for the client, as specified in RFC 1001/1002 |
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To change this default list, options which are to be sent out by Windows CE are read from the registry on a per adapter basis under the following key:
HKEY_LOCAL_MACHINE\Comm\<adapter name>\Parms\TcpIp\DhcpOptions
Values are created under this key that have the names of the options to request. The default ("@") value under the DhcpOptions key must also be defined.
The registry setting format is a binary structure equivalent to the actual DHCP option encoding (as per RFC 1533), a one-byte code, followed by a one-byte length value, followed by the actual data. Example: The following setting (in .REG file notation) shows requesting the value for the subnet mask option:
HKEY_LOCAL_MACHINE Comm\<adapter name>\Parms\TcpIp\DhcpOptions
@=""
"1"
After DHCP has retrieved the information from the server, you might find the following under the value "1" above:
This corresponds to a subnet mask of 255.255.255.0. (type 1, length 4, data 0xFFFFFF00). Send Options
Windows CE version 2.12 (with QFE fix #1 applied) and later also supports the capability to supply data to send options to the server. The most common case requiring this is the sending of the host name option.
The key for the send options is as follows:
HKEY_LOCAL_MACHINE\Comm\<adapter name>\Parms\TcpIp\DhcpSendOptions
Values are created under this key which have the names of the options to send. The default ("@") value under the DhcpOptions key must also be set. The format of the option data must include type and length fields, as specific by RFC 1533. Windows CE does not attempt to parse the data, it just copies it into the packet. Example: The following example setting shows how to set the host name option (12) to the value "myhost":
HKEY_LOCAL_MACHINE\Comm\<adapter name>\Parms\TcpIp\DhcpSendOptions
@=""
"12"=hex:0c,06,6d,79,68,6f,73,74
REFERENCES
World Wide Web Consortium ( http://www.w3.org) Request for Comment documents RFC2131 and RFC1533
| Modification Type: | Minor | Last Reviewed: | 11/22/2005 |
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| Keywords: | kbinfo KB290279 |
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