DCNSA Level III

Network Troubleshooting flashcards

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Complete Flashcard Reference

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In what order does the network diagnostic procedure work through its checks?

1. Check the hardware: cables, power, link lights. 2. ipconfig (or ifconfig) to confirm the IP configuration. 3. ping and tracert to confirm connectivity and trace where it fails. 4. A DNS check (nslookup). 5. Contact the ISP if the fault is outside the network. 6. Check for virus and malware infection. 7. Review the system logs. Quickest and most local first, most involved and most external last.

A ping to an external IP address gets replies, but a ping to the same destination by its domain name fails. What is the fault?

DNS name resolution. The IP-address ping proves connectivity works at the IP level, so only the name lookup is failing. Run nslookup next to confirm which DNS server is failing to resolve the name.

What four stages does a fault pass through before it can be fixed?

Fault reporting, fault detection, fault classification and fault location. Treating them as one undifferentiated step is what makes troubleshooting feel chaotic rather than systematic.

How does network maintenance differ from troubleshooting?

Maintenance is the ongoing routine work that keeps a network healthy: scheduled and preventive. Troubleshooting is the structured process of finding and fixing the cause of one specific, already-reported fault: reactive and fault-specific.

What does tracert (traceroute) show that ping does not?

The path a packet takes to its destination, hop by hop. That locates where along the path a failure or a significant delay occurs, rather than only confirming that one exists somewhere.

What does netstat show, and when is it the right tool?

The active network connections and listening ports on a device. Use it to confirm whether a service is actually running and listening, or whether an unexpected connection is present, such as software suspected of secretly sending data out to the internet.

ipconfig shows a device with an address starting 169.254. What does that indicate?

An APIPA fallback address. The device could not reach a DHCP server and assigned itself an address, so the fault points at DHCP.

What four things should a complete set of network documentation cover?

1. A current topology diagram. 2. The IP addressing scheme and subnet allocations. 3. A device inventory. 4. The change history.

What do automated documenting tools such as NetBrain do, and why are they valuable?

They automatically discover and diagram a live network. That keeps documentation accurate and current with far less manual effort than hand-maintained diagrams, which matters most once a network grows too large to document reliably from memory.

What must testing confirm before a fault is closed?

That the fix actually resolved the original symptom, and that it did not introduce a new problem elsewhere. A fault reopened days later because the fix was never verified erodes confidence in the whole troubleshooting process.

Why is the hardware checked before any software or configuration fault is assumed?