Broadcast name resolution
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
Broadcast name resolution
If you enable broadcast name resolution on a server running Routing and Remote Access, a remote access client can resolve full computer names and NetBIOS names of computers and other resources on a remote network that does not have either a DNS or a WINS server configured. This feature requires no configuration of the remote access clients, and it is enabled by default on the remote access server.
When broadcast name resolution is enabled, the remote access server uses a NetBIOS over TCP/IP (NetBT) proxy to resolve names as follows:
A remote access client that must resolve a name to an IP address broadcasts a NetBIOS Name Query packet across all interfaces.
The remote access server receives the NetBIOS Name Query packet and checks its cache for the appropriate mapping of name to IP address.
If the remote access server has the appropriate mapping, it sends a NetBIOS Name Query Response packet to the remote access client.
If the remote access server does not have the appropriate mapping, it broadcasts the NetBIOS Name Query packet on all its LAN interfaces. The resource whose name is being resolved sends a NetBIOS Name Query Response packet to the remote access client.
After the remote access server routes the NetBIOS Name Query Response packet from the resource to the remote access client, the mappings remain in the cache of the server for a limited period of time. The default period of time is 10 minutes.
After this point, the remote access client uses the IP address of the resource to send packets to that resource.
As a result, a remote access client can resolve names of resources on a remote network as if the remote access client were on the same LAN as the resources.
By default, broadcast name resolution allows remote access clients to resolve names on a remote network but not for resources on a LAN to resolve the names of remote access clients. Remote access servers with broadcast name resolution enabled do not, by default, broadcast NetBIOS Name Query packets to interfaces that connect to the Internet. Unless you change this behavior, a remote access client cannot resolve the name of another remote access client. If you have a network that averages 10 connections or fewer, you might want to change this behavior.
A broadcast name resolution example
Remote Access Client A has established a connection to the remote access server for a small business network. The remote access server has three LAN interfaces (LAN1, LAN2, and LAN3) and an external interface. One of the resources on the small business network is Network Printer B, which is accessed through LAN3. Remote Access Client A has the NetBIOS name but not the IP address of Network Printer B. Remote Access Client A broadcasts a NetBIOS Name Query packet for Network Printer B. The remote access server broadcasts the NetBIOS Name Query packet to LAN1, LAN2, and LAN3 but not to the external interface. Network Printer B responds with a NetBIOS Name Query Response packet that is addressed to Remote Access Client A. The remote access server routes the NetBIOS Name Query Response packet to Remote Access Client A.