DHCP and WINS

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WINS is a naming service used to register and resolve name-to-address mappings for NetBIOS clients on TCP/IP-based networks.

Because NetBIOS naming is a required feature for networking that is supported in all previous versions of Windows, install and use WINS if you are operating the Windows 2000 DHCP service in a network environment that includes DHCP clients running under any of the following earlier Microsoft operating systems:

  • Windows for Workgroups 3.11

  • Windows 95

  • Windows NT Advanced Server 3.1

  • Windows NT 3.5 x

  • Windows NT 4.0

  • MS-DOS client for Microsoft Networks

In many cases, it is not necessary to add WINS servers beyond the number of servers that are planned for DHCP server usage. In many cases, the same server computer can work effectively as both the WINS and DHCP server for a single internet on your network.

Where a single server is configured as both a WINS server and a DHCP server, it can:

  • Administer a defined scope or superscope range of IP addresses for your network.

  • Serve as the default gateway to provide IP forwarding between adjoining physical networks.
    To set the same default gateway for all DHCP clients located across subnets, assign DHCP option code 3 by using the server computer's IP address as the value in configuring the DHCP scope options.

  • Serve as the primary WINS server for adjoining physical networks.
    To set the WINS server for all DHCP clients located across subnets, assign DHCP option code 44 (a list of IP addresses for WINS servers) and use the server computer's IP address as the value.
    To ensure that WINS is used first by all DHCP clients for NetBIOS name resolution (before broadcast name resolution is tried), assign option code 46 (WINS/NBT node type) to identify the WINS node type as h-node (hybrid node).

Adding Fault Tolerance to DHCP/WINS Service

To create a more fault-tolerant installation for DHCP and WINS, you can set up two server computers running Windows 2000 Server to act as backup service providers for each other. Table 4.12 shows the functions of each server (Server1 and Server2) when configured in this way.

Table 4.12 DHCP/WINS servers

Computer Name

WINS Server Status

DHCP Server Status

Server1

Primary WINS

Secondary DHCP

Server2

Secondary WINS

Primary DHCP

If you want to create a primary and backup relationship between DHCP servers, you can partition the address pool so that each server provides addresses to remote clients. One recommended practice is to allocate approximately 75 percent of the available IP address pool for your network to the primary DHCP server and the remaining 25 percent of your address pool to the backup DHCP server.

When defining a shared scope between two DHCP servers, you must ensure that the scope is configured to be disjointed (with no overlap) for each server, to avoid duplicating IP addresses in lease offerings for both servers.

Additional Recommendations

When using DHCP and WINS together on your network, consider the following options for interoperation:

Use additional DHCP scope options.    Use DHCP options to assign WINS node types (option type 46) and to identify WINS servers for use by DHCP clients (option type 44). In some cases, this can involve adjusting these option types for each physical subnet where DHCP and WINS are implemented.

Assign a length of time for DHCP lease durations comparable to the time WINS uses for renew intervals.    By default, DHCP leases are eight days in length and the WINS renew interval is six days. If lease lengths for DHCP differ widely from WINS renew intervals, the effect on your network can be an increase in lease-management traffic and might cause a WINS registration for both services. If you shorten or lengthen the DHCP lease time for clients, modify the WINS renew interval accordingly.

Configure all installed connections as routable interfaces.    Windows 2000 does not guarantee the binding order for NetBIOS when more than one connection is present and active. All multihomed WINS servers should have their primary IP addresses assigned to each network connection. When configuring a replication partner with the multihomed server as a push or pull partner, you can ensure that the partner always connects to the same adapter on the multihomed server by configuring the partner to refer to the multihomed server using the specific IP address to which you want the partner to connect. If the partner is configured to refer to the name of the multihomed server instead of a specific IP address, when the replication partner resolves the name to an IP address, it may end up sending WINS packets to the multihomed server using any of its IP addresses.