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Windows Network Administration

Chapter 5:Troubleshooting Name Resolution

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Common NetBIOS Name Resolution Problems

• Three categories of NetBIOS problems:

1. Name resolution problems:– Examine node type first

2. Browsing problems– First identify scope, e.g.:

• Inability to browse entire network• Inability to browse single system

3. Name registration problems– First determine whether there is a

naming conflict

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Examining Computer Browser Service

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Common DNS Resolution Problems

• For client configuration problems:– Examine DNS configuration on client

• Ipconfig• Properties dialog box for network interface

• For server configuration problems:– Problems with local zones

• Check server database for record • Protocol analyzer

– Problems with remote zones• Clear DNS server cache or restart service• Examine resolution chain

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Clearing the Cache

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Using ping, ipconfig, and nbtstat

• Additional troubleshooting– Validate problem is name resolution

• ping command

– Determine whether cause is on client side

• ipconfig/all command

– Check (if necessary clear) NetBIOS or DNS name cache

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pingA successful resolution attempt

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pingA failed resolution attempt

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nbtstat• nbtstat – c

– Displays NetBIOS name cache

• nbtstat – R– Purges and reloads NetBIOS name cache

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ipconfig

• ipconfig /displaydns• ipconfig /flushdns• ipconfig /registerdns

• net stop dnscache• net start dnscache

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ipconfig

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ipconfig

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nslookup

• Allows custom queries to DNS servers• Interactive mode:

– Custom nslookup prompt• Configurable• Allows multiple queries

• Non-interactive mode:– Run single command-line query

• Syntax– nslookup [-option] [host name to resolve]

[server to use]

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nslookup: Non-Interactive Query

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nslookup: Entering Interactive Mode

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Interactive Mode: Resolving a Name

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Interactive Mode: Available Options

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Interactive Mode: Available Options

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nslookup: set debug

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nslookup: set type

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nslookup: Basic ls Listing

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ls Listing Specifying SRV Type

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Examining NetBIOS Name Resolution

• Only broadcasts and WINS can be examined with a protocol analyzer

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Examining DNS Name Resolution

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Examining DNS Name Resolution

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Examining DNS Name Resolution

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Summary

• NetBIOS problems fall into three categories:– For name resolution problems, examine node

type first. – For browsing problems, first identify the scope. – For name registration problems, first verify there

is a naming conflict.

• Two basic types of DNS problems: client configuration problems and server configuration problems.

• Two basic types of DNS server configuration problems: problems with local zones and problems with remote zones.

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Summary

• Steps in troubleshooting name resolution problems include using ping to validate problem, using ipconfig /all to validate client configuration problem, and using nbtstat to check or clear NetBIOS or DNS name cache.

• nslookup: Diagnostics command for crafting custom queries to DNS servers with modes: interactive and non-interactive.

• Key to troubleshooting at packet level: Understanding traffic you are analyzing; knowing what to expect in order to understand why the correct activity is not occurring.