Network Comm. Across Router Using PC-TCP and LAN Manager (87667)

CAUSE

The NetBIOS uses broadcasts for name claims, name resolution, and nondirected datagrams. The RFCs 1001 and 1002 define three ways in which broadcast traffic can be handled by a NetBIOS over TCP/IP implementation. These are B-Node (Broadcast), P-Node (Point-to- Point), and M-Node (Mixed). B-Node uses broadcasts for name contention and resolution. B-Node broadcasts for name contention and name resolution do not go through a router. A router will not allow a broadcast message to pass through to other networks.

FTP Software's implementation of NetBIOS over TCP/IP is purely B-Node based. Therefore, the B-node broadcasts will not go across a router and network communications will not take place across the router.

On the other hand, Microsoft's implementation of NetBIOS is also B-node based. However, the MS TCP/IP stack uses the LMHOSTS file in LAN Manager to provide the NetBIOS-name-to-IP-address mapping. The LMHOSTS file is located in the <LANROOT>\ETC directory. By entering the NetBIOS name to IP address mapping in the LMHOSTS file, the RFC NetBIOS name query request frames for those names will not be sent to the local network. Instead, the cache containing the entries in LMHOSTS file will be used to resolve the NetBIOS-name-to-IP-address mapping. Therefore, broadcasts will not be generated and the machines will be able to communicate across a router.