Chapter 5: Configuring and using NetBIOS

Table of contents

• Chapter 5: Configuring and using NetBIOS
  • Configuration considerations over TCP/IP
  • Verifying broadcasts
  • Setting the scope identifier
  • Viewing NetBIOS status

Chapter 5

Configuring and using NetBIOS

Configure NetBIOS with the Network Configuration Manager as described in ``Configuring protocols'' in Configuring Network Connections. When you do, you configure:

• The local host name, IP address, and broadcast address used by NetBIOS.

• The NetBIOS scope identifier, described later in this chapter.

• A number of per-user variables, such as the number of default sessions, maximum names, and maximum commands.

• The maximum IP datagram size handled by NetBIOS.

NetBIOS has special considerations when running with TCP/IP as described in the following sections. For example, the format of the /etc/hosts file can vary from one vendor's TCP/IP to another. If you modify this file, be sure to follow the correct format of that machine. The way broadcast messages are handled can also vary from one vendor's TCP/IP to another. Investigate any differences among the various versions of TCP/IP on your network and the methods for resolving those differences. Finally, be sure that the NetBIOS scope identifier has the same value on all the computers running NetBIOS and TCP/IP on the same network.

Verifying broadcasts

Broadcasts allow TCP/IP to send certain types of messages, such as alerts, to a wide audience on a LAN. NetBIOS uses broadcasts 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 nbstatus command on the local client machine, and also on the remote machine if the nbstatus command is available on that machine. The nbstatus command with no arguments should return NetBIOS status information if NetBIOS is running on the local machine.

1. Verify that the network and subnet portions of the IP address are the same on all computers. Broadcasts do not repeat across 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 on the ifconfig command line in the /etc/tcp file. You must reboot the machine so that the changes made to /etc/tcp file take effect. To configure the IP address in another implementation of TCP/IP, refer to the documentation for that implementation.

2. 
   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 is specified on the ifconfig command line in the /etc/tcp file by using 255 for each byte of the host portion of the IP address. For example:

   ifconfig net0 10.0.118.1 broadcast 10.0.118.255 netmask 255.255.255.0
   

   The network portion of the address in the preceding example is 10.0.118, and the host portion is set to all ``1''s by appending 255 to the network portion. If you change the /etc/tcp file, you must reboot before the changes take effect.
   

3. 
   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 this is a problem, 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 follows:

   ifconfig e3A0 10.0.118.1 broadcast 10.0.255.255 netmask 255.255.255.0
   

   If you change the broadcast address, reboot the machine to have the changes take effect.
   

4. Verify that NetBIOS is working by using the form of the nbstatus command that requests status from a remote computer. For example, to verify that NetBIOS is working on the machine on your network named fred, enter the command nbstatus FRED
   Note that the computer name is specified in all uppercase letters. If NetBIOS is functioning between the two machines, a list of information about the remote computer will be displayed. If an error is returned, this indicates that NetBIOS is not working, either because there is still a TCP/IP broadcast incompatibility, or because different NetBIOS scope identifiers are being used. Note that it is sometimes possible for the remote form of the nbstatus command to return an error under normal circumstances. Some implementations of NetBIOS do not accept the remote adapter status NCB(Network Control Block); also, if the remote machine is a LAN Manager for UNIX Systems client, and there currently are no sessions between the client and a server, then NetBIOS status is not returned.

The NetBIOS scope identifier is a string of characters used when network applications communicate using NetBIOS over TCP/IP. The NetBIOS scope identifier must be the same for all computers on a NetBIOS network using TCP/IP as the transport. If you have different scope identifiers on your computers, NetBIOS assumes they are part of a different logical network, and cannot connect to them.

You set the scope identifier when using the Network Configuration Manager to configure NetBIOS. Before setting it, check its value on the other machines in the network. If you have MS-DOS or OS/2 workstations on the network, the NetBIOS scope identifier should be set to NULL on all machines on the network. Many implementations of NetBIOS for TCP/IP allow you to use only the NULL scope identifier.

If you have any other LAN Manager-compatible machines on the network, check their documentation for restrictions.

The scope identifier's setting depends on the implementation of TCP/IP. SCO TCP/IP sets the scope identifier with the NB_SCOPE parameter in the file /etc/default/nbconf. A typical example of the scope identifier's syntax would be:

   NB_SCOPE=""

The nbstatus
command provides NetBIOS status. For example, it can rreport the status from LAN Manager client or from a remote LAN Manager server. LAN Manager client must be started and have at least one connection to a server before NetBIOS status can be obtained.

The output from nbstatus resembles the following display:

   Adapter status for adaptor 0, name *:
   ID: 08 00 14 51 62 09 (655364)  Jumpers 0  Selftest 0  Version 1.0
   Time up 5:51
   Packets sent:             2176       CRC errors:                 0
   Packets received:        99060       Alignment errors:           0
   Retransmitted packets:       0       Collisions:                 0
   Resources exhausted:         0       Aborted transmissions:      0
   Ncbs:      Free  :  45 of  48;  maximum configurable:  48
   Sessions:  In use:   2 of  48;  maximum configurable:  48
   Adapter packet size:  2048
   Local name table (2 names):
   Name            Soc Num Status
   KIWI            x00   3 0x4
   

   Session status for adaptor 0, name *:
   name num 255, # sessions 3, rcv dg=1, rcv any=0
   LSN   State   Local Name   Soc   Remote Name   Soc   rcvs   sends
   1     ESTAB   KIWI         x00   CHERRY        x20   0      0
   2     ESTAB   kiwi         x73   cherry        x73   1      0

The next item, the local name table, shows the names that have been added to NetBIOS. The fields are as follows:

Name

Name in use

Soc

Numeric value of the 16th character of the name. By convention, uppercase names are used in the SMB filesharing protocol, and lowercase names are used by other LAN Manager utilities. The significance of the Soc field is defined by the NetBIOS application. The SMB protocol uses this field to indicate a particular service or function. For example, the LAN Manager client uses the machine name in uppercase with a Soc value of 0x00 (ASCII code for the null character) to connect to the remote filesharing server.

Num

Number assigned to the name by NetBIOS when the name was added to the table.

Status

Status of the name that NetBIOS has added or is adding to the name table. Valid numbers have the following definitions:

0x0

NetBIOS is trying to register a name in the local name table

0x4

NetBIOS has successfully registered this name in the local name table

0x5

NetBIOS has de-registered this name from the local name table

0x6

NetBIOS has detected a duplicate name in the local name table

0x7

NetBIOS has detected a duplicate name with de-register pending

0x84

name is a group name

LSN

NetBIOS local session number (LSN) for the session

State

state of the session. Possible states are:

LISTEN

Waiting for a connection

CALL

Attempting to connect

ESTAB

An established connection

CLOSING

Connection is in the process of closing

CLOSED

Connection is closed

ABORT

Connection has been aborted

Local Name

Local name associated with the session

Soc

Numeric value of the 16th character of the name

Remote Name

Server name associated with the session

Soc

Numeric value of the 16th character of the server name

rcvs

Number of RECEIVE NCBs outstanding on the session

sends

Number of SEND NCBs outstanding on the session

   Ncbs:	   Free  :  45 of  48;	maximum configurable:  48

To obtain adapter status from remote machines, you can use the nbstatus MACHINE command. MACHINE is the name of the remote machine in all uppercase letters.

For more information on using nbstatus, see ``Viewing NetBIOS status'' and nbstatus(LMC).