RAS Server Behavior When Configured to Use DHCP to Assign IP Addresses

ID: Q216805

The information in this article applies to:

Microsoft Windows 2000 Server

SUMMARY

A Windows 2000 RAS server behaves differently than a Microsoft Windows NT 4.0 server when it is configured to use Dynamic Host Configuration Protocol (DHCP) to assign remote IP addresses.

MORE INFORMATION

Behavior When a DHCP Server Is Available

The RAS server uses DHCP to lease IP addresses in blocks of 10 and stores them in the registry. The server leases additional addresses in blocks of 10 as needed. The number of addresses that RAS leases at a time is configurable in the registry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RemoteAccess\Parameters\IP

Value Name: InitialAddressPoolSize
Data Type: REG_DWORD
Default: 10

This is different from the Windows NT 4.0 behavior of leasing enough IP addresses for all the RAS devices (modems, ISDN, and PPTP) configured on the RAS server, plus one address for the RAS server interface. Therefore, if you have 20 modems configured on your RAS server in Windows NT 4.0, the RAS server leases 21 IP addresses when the RAS service starts.

Behavior When a DHCP Server Is Not Available

The RAS server uses Automatic Private IP Addressing (APIPA) to assign IP addresses to RAS clients. These addresses are randomly chosen from the 169.254.0.0/16 subnet.

This is different from the Windows NT 4.0 behavior. If a Windows NT 4.0 server cannot contact a DHCP server, it does not have IP addresses to assign to RAS clients. The clients then cannot connect using TCP/IP.

The RemoteAcess Service will generate the following event:


Event 20169

Source RemoteAccess
Type Warning

Description:

Unabled to contact a DHCP server. The Automatic Private IP Address <Autonet address> will be assigned to dial-in clients.  Clients may be unable to access resources on the network.

Additional query words: RRAS 169.254.0.0 Autonet

Keywords : kbenv
Version : WINDOWS:2000
Platform : WINDOWS
Issue type : kbinfo