Cisco CCNA Certification Exam Tutorial DNS And The IP Name-Server Command
Below is a MRR and PLR article in category Computers Technology -> subcategory Computer Certification.
Cisco CCNA Certification Exam Guide: DNS and the IP Name-Server Command
Overview
Understanding DNS behaviors is crucial for both the CCNA exam and practical network management. In this guide, learn how to effectively utilize the `ip name-server` command, presented by Chris Bryant, CCIE
12933.
Key Concepts
DNS on Cisco Routers
When a command is mistyped on a Cisco router, it tries to resolve it using DNS. Initially, the router checks the local IP Host table, as indicated by the "translating" message. If no relevant entry is found, the router broadcasts a request to a remote DNS server. To stop this broadcast, use the global command `no ip domain-lookup`. If you need DNS resolution, ensure `ip domain-lookup` is enabled.
Example Scenario
1. Mistyped Command Behavior
- Command: `R2
contin`
- Output:```
Translating "contin"...domain server (255.255.255.255)
% Unknown command or computer name, or unable to find computer address
```
- Explanation: Without a local IP Host table, the router sends a broadcast. The attempt must time out before proceeding.
2. Disabling DNS Lookup
- Command:
```
R2
conf t
R2(config)no ip domain-lookup
R2contin
```- Output:
```
Translating "contin"
% Unknown command or computer name, or unable to find computer address
```
- Explanation: The router acknowledges the absence of local resolution and promptly indicates the name cannot be resolved.
3. Enabling DNS Lookup with a Specific Server
- Command:
```
R2
conf t
R2(config)ip domain-lookup
R2(config)ip name-server 10.1.1.1
R2contin
```- Output:
```
Translating "contin"...domain server (10.1.1.1)
```
- Explanation: With `ip domain-lookup` enabled and the DNS server set to 10.1.1.1, the router knows exactly where to resolve names.
Conclusion
Setting up a Cisco router to use a specific DNS server is straightforward. By mastering the `ip name-server` command, you enhance both exam readiness and practical network troubleshooting.
You can find the original non-AI version of this article here: Cisco CCNA Certification Exam Tutorial DNS And The IP Name-Server Command.
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