[This is pre-release documentation and subject to change in future releases. This topic's current status is: Milestone-Ready]

Topic Last Modified: 2010-07-15

The DHCPConfigScript.bat tool can be used if configuring DHCP Options on a Windows DHCP server. If you plan to use other DHCP servers in your deployment, check the DHCP Servers documentation on how to configure then options. The following section describes these DHCP options in more detail, including how you can use DHCPUtil.exe to obtain the byte values that are required to set the DHCP option values.

DHCP Option 120

  • 0 – encoding type (Only Unified Communications clients understand this option)

  • Following the encoding type, the general pattern is the length of a portion of the FQDN followed by ASCII codes (for example 97 for a) for the corresponding characters.

  • Each character in the example (like “e”) is actually 1 byte with a value that is equal to the ASCII code for the respective character.

  • You can use DHCPUtil.exe to obtain the value for DHCP Option 120. Note that DHCPUtil only supports specifying up to one Communications Server Pool FQDN.

More details about DHCP Option 120 are in RFC 3361.

DHCP Option 43

Microsoft Communications Server 2010 and the IP phone clients use DHCP Option 43 by including a new vendor class identifier. This is specified as DHCP Option 60 (RFC 2132, Section 9.13). For discovering the Communications Server Certificate Provisioning Service, the IP phones set the DHCP Option 60, which is the vendor class identifier to MS-UC-Client (case-sensitive).

DHCP Option 43 is made up of the following vendor-specific sub-options. For discovery of Communications Server Certificate Provisioning Service, here are the sub-options that have to be configured:

  • Id= 1, value =4D532D55432D436C69656E74, description = MS-UC-Client

  • Id=2, value=6874747073<Can vary with deployment, but generally is constant >, description=URL Scheme

  • Id=3, value=<varies with deployment>, description=Communications Server Internal Web FQDN

  • Id=4, value=343433 (Can vary with deployment, but generally is constant), description=Communications Server Web Server Port

  • Id=5,value=< /CertProv/CertProvisioningService.svc - 2F4365727450726F762F4365727450726F766973696F6E696E67536572766963652E737663>, description=Relative Path to the Communications Server Certificate Provisioning service

Using DHCPUtil.exe to obtain DHCP Option 120 and 43 values

You can use DHCPUtil.exe to obtain the value for various sub-options for Option 43.

DHCPUtil.exe -SipServer <Communications Server Pool FQDN > -WebServer <Communications Server Internal Web FQDN> -RunConfigScript.

The Communications Server Internal Web FQDN is the FQDN of the Web Components That Run on the Communications Server pool. This is typically specified by using Topology Builder as part of pool properties. If you do not use DNS Load Balancing for the pool, the Communications Server Internal Web FQDN is the same as the Communications Server pool FQDN.

Copy Code 
Sip Server FQDN: ocspool1.contoso.com
Certificate Provisioning Service URL: https://ocspool1.contoso.com:443/CertProv/CertProvisioningService.svc

DHCP Option 120 Value:
00076578616D706C6503636F6D00

DHCP Option 43 Value:
Vendor Class Identifier: MS-UC-Client
Option 43 (for vendor=MS-UC-Client):
			 sub-option 1 <UC Identifier>: 4D532D55432D436C69656E74
			 sub-option 2 <URL Scheme>: 6874747073
			 sub-option 3 <Web Server FQDN>: 6F6373706F6F6C312E636F6E746F736F2E636F6D
			 sub-option 4 <Port>: 343433
			 sub-option 5 <Relative Path for Cert Prov>: 2F4365727450726F762F4365727450726F766973696F6E696E67536572766963652E73763

You can use the values that are provided by the DHCPUtil.exe tool above to then configure your DHCP server. For a DHCP server other than provided by Windows, check the DHCP server vendor documentation.

See Also