Testing NetBIOS Name Resolution by Establishing a Session

Select Certification Bootcamp :
MCSE MCSE+Security CCNA CCNP RHCE Register Course Fees Home

Leading MCSE, CCNA, CCNP Certification boot camp training provider in India, USA, UK.

Testing NetBIOS Name Resolution by Establishing a Session

The ultimate test of connectivity is to establish a session with another host. If you can establish a session through mapping a drive or by executing a Net Use command (which is the command-line equivalent of mapping a drive), you have made a NetBIOS connection. If you can FTP, Telnet, or establish a Web session with another host, you have made a Sockets connection. A NetBIOS connection or a Sockets connection are the two main types of connections made by a TCP/IP client.

After the drive has been mapped with Net Use, you can switch to the new drive letter, view files and directories, and do any other things that are specified in the permissions of the share mapped to the drive letter. To get more information about the syntax of the Net Use command, type net help use in a command prompt.

A common problem in making NetBIOS connections is that the wrong NetBIOS name is used. Verify that the destination host has the same name that you are using to make the connection. Another potential problem with the name configuration occurs when NetBIOS scope IDs are used. Only NetBIOS hosts with the same scope ID can communicate with each other.

The scope ID is configured through the advanced TCP/IP parameters. Incorrect share permissions can prevent you from establishing a NetBIOS session. When you try to connect a drive to a share where you have No Access, you receive an Access Denied message. This message indicates that you can connect to the server, but your rights did not allow you to make a connection to this specific share. This type of failure has nothing to do with TCP/IP connectivity. Remember that if the administrator changes your permissions to give you access, and you want to try again, you must log out and log in again to receive a new access token with the updated permissions.

To resolve NetBIOS connectivity problems, you must know what sources are used to resolve NetBIOS names. The first place a client looks to resolve a NetBIOS name is the local cache. You can view the contents of the NetBIOS cache with the NBTSTAT command. You should verify that no incorrect entry is in the cache that maps the NetBIOS name to an incorrect IP address. If there is, however, you can remove the entry and then try to make another connection.

The next place to attempt NetBIOS name resolution is in a query to a WINS server. The client must be configured to be a WINS client. You can verify the address of the WINS server through the Advanced properties of TCP/IP or by using IPCONFIG /all. You can view the contents of the WINS database by using WINS Manager on the WINS server. Verify that the host name is in the database and, if so, make sure it is mapped to the correct IP address.

If the WINS server is configured to do a DNS lookup, you have another way to get NetBIOS resolution. The WINS server queries DNS if the WINS server cannot resolve the name from its own database. You can view the contents of the DNS database files by using DNS Manager on the DNS server or by using the NSLOOKUP utility from any client.

The client next tries a broadcast to resolve NetBIOS names, although you cannot configure what the client finds through the broadcast. The next place the client looks for NetBIOS name resolution is the LMHOSTS file. You can configure the contents of this file. The client must be configured for LMHOSTS lookup in the advanced TCP/IP configuration. Also, the LMHOSTS file must be located in the correct directory path. On an NT computer, the LMHOSTS file must be in the path <winnt root>\ system32\etc.

Next, verify the entries in the LMHOSTS file. The correct host name and IP address must be entered in this file. If you have multiple entries in the file for a host name, only the first entry is used. If you added another entry for a host in the file, you must delete the other entry listed earlier in the file so that it will not be used.

Domain names are another source of potential problems with LMHOSTS files. The domain name must be registered with the IP address of the Primary Domain Controller (PDC) and #DOM (a switch that registers the server as a domain controller) on the same line. This entry is necessary to log on to the domain as well as to see the domain in a browse list.

Another problem with LMHOSTS files doesn’t prevent connectivity, but it can greatly delay it. If you have #INCLUDE statements at the top of the LMHOSTS file, the files specified by #INCLUDE are included first before any other entries lower in the LMHOSTS file are searched. You can speed connections to hosts entered in the LMHOSTS file by moving the #INCLUDE entries to the bottom of the LMHOSTS file.

Vibrant Advantage :

No Prestudy
Longest Duration Camp
Chalk Talk Training
Highest Passing Rate
Bootcamp since 1999
Guaranteed Certification ...

Testimonials :

MCSE Certification boot camp

The instructor taught real world experience and did not just teach us to pass the test. He knew the subject well and was encouraging. His lectures were very well delivered....

Colver Dennis, USA