Configuring and using NetBIOS

Verifying broadcasts

Broadcasts enable TCP/IP to send certain types of messages, such as alerts, to a wide audience on a directly attached LAN. NetBIOS can use the broadcast mechanism for tasks such as name registration. The following steps will help ensure that broadcasting is working correctly, with the assumption that TCP/IP and NetBIOS are running on both the local and remote machines. It should be possible to run the local form of the nbtstat(1Mtcp) command on the local client machine, and also on the remote machine if the nbtstat command is available on that machine. The nbtstat command with no arguments should return NetBIOS status information if NetBIOS is running on the local machine.

Verify that the network and subnet portions of the IP address are the same on all computers. Broadcasts are not forwarded between networks or subnets, so the network and subnet addresses must be identical. The configuration of IP addresses varies according to the specific implementation of TCP/IP. In SCO TCP/IP, the local IP address is configured using the Network Configuration Manager. If you change an IP address, you must shutdown and reboot so that the changes can take effect. To configure the IP address in another implementation of TCP/IP, refer to the documentation for that implementation.
Verify that all computers on the network agree on either all ``0''s or all ``1''s for the broadcast address. Using all ``1''s is recommended. In SCO TCP/IP, the broadcast address can be displayed by using the ifconfig -a command. This is an example of what the ifconfig output may look like:
```
net0: flags=23<UP,BROADCAST,NOTRAILERS> mtu 1500
	inet 172.16.118.1 netmask ffffff00 broadcast 172.16.118.255
lo0:  flags=49<UP,LOOPBACK,RUNNING> mtu 2048
	inet 127.0.0.1 netmask ff000000
```
The network portion of the address in the preceding example is 172.16.118, and the host portion is set to all ``1''s by appending 255 (0xff) to the network portion. If you modify the broadcast address, you must shutdown and reboot so that the changes can take effect.
Verify that all computers agree on the broadcast address relative to the subnet mask. Some implementations of TCP/IP ignore the subnet portion of class C IP addresses. If you have such an implementation, replace the subnet number with the broadcast number when defining the broadcast address. Using the same example as in step 2, where the subnet portion is 118, the broadcast address would be configured as 172.16.255.255. The output from the ifconfig -a command would look similar to the output shown below:
```
net0: flags=23<UP,BROADCAST,NOTRAILERS> mtu 1500
	inet 172.16.118.1 netmask ffffff00 broadcast 172.16.255.255
lo0:  flags=49<UP,LOOPBACK,RUNNING> mtu 2048
	inet 127.0.0.1 netmask ff000000
```
If you change the broadcast address, shutdown and reboot to make sure the changes take effect.
Verify that NetBIOS is working by using the form of the nbtstat command that requests status from a remote computer. For example, to verify that NetBIOS is working on your machine, enter the command:

nbtstat
Provided that NetBIOS is running on your system, statistics are displayed. If NetBIOS is not running, an error message is displayed instead.
To verify that NetBIOS can communicate with a remote system, use the following form of the nbtstat command:

nbtstat -a remote_system_name
If NetBIOS can communicate between two systems, statistics about the remote system are displayed. If an error is returned, this indicates that NetBIOS is not working. This may be because there is still a TCP/IP broadcast incompatibility, or because different NetBIOS scope identifiers are being used.