Friday Study Session Flashcards
(15 cards)
Q: A host has an IP address but cannot reach websites by name. What’s the most likely cause?
- Incorrect subnet mask
- DNS failure
- DHCP server offline
- NAT overload
Correct Answer: DNS failure
Explanation: DNS translates domain names into IP addresses. If IPs work but names don’t, it’s a DNS issue.
Practical Use: Compare ping 8.8.8.8 to ping google.com to confirm.
Why Others Are Incorrect:
- Subnet mask would block local comms too.
- DHCP is not involved post-IP assignment.
- NAT impacts external access, not name resolution.
Objective: DNS troubleshooting
Follow-up: What command tests DNS directly in Windows?
Q: A user receives a 169.254.x.x address. What does this indicate?
- Valid static IP
- Successful NAT
- DHCP server unreachable
- DNS conflict
Correct Answer: DHCP server unreachable
Explanation: A 169.254.x.x address is APIPA, used when DHCP fails.
Practical Use: Check server availability or IP scope exhaustion.
Why Others Are Incorrect:
- It’s not static, NAT, or DNS related.
Objective: DHCP error recognition
Follow-up: What command can you use to request a new IP address?
Q: What command shows the current DNS server assigned to a Windows host?
- nslookup
- ipconfig /all
- ping
- netstat
Correct Answer: ipconfig /all
Explanation: This command reveals detailed interface config including DNS servers.
Practical Use: Identify DNS misconfiguration quickly.
Why Others Are Incorrect:
- nslookup tests DNS, doesn’t show config.
- Ping and netstat don’t reveal DNS info.
Objective: IP config visibility
Follow-up: What does a DNS of 0.0.0.0 indicate?
Q: What tool shows if DNS is resolving domain names properly?
- ipconfig
- netstat
- nslookup
- arp -a
Correct Answer: nslookup
Explanation: It tests domain-to-IP resolution directly.
Practical Use: Confirm DNS health independently.
Why Others Are Incorrect:
- Other tools show network or IP info, not DNS testing.
Objective: DNS verification
Follow-up: What’s a Linux alternative to nslookup?
Q: A video call suffers jitter and packet delay. What’s the best command to diagnose?
- ping -t
- show interfaces
- nslookup
- ipconfig
Correct Answer: ping -t
Explanation: This monitors latency over time, revealing jitter patterns.
Practical Use: Watch for spiking delay between pings.
Why Others Are Incorrect:
- Interfaces show link health.
- DNS and config won’t help here.
Objective: Performance metric diagnosis
Follow-up: What follow-up tool shows path and delay hop-by-hop?
Q: What does show interfaces reveal that helps diagnose performance issues?
- VLAN IDs
- Packet errors, CRCs, drops
- NAT table
- DNS queries
Correct Answer: Packet errors, CRCs, drops
Explanation: Reveals physical layer issues impacting throughput.
Practical Use: Identify bad cables or faulty NICs.
Why Others Are Incorrect:
- VLANs and DNS require other tools.
- NAT tables are unrelated.
Objective: Interface analysis
Follow-up: What might a high number of CRC errors indicate?
Q: A router shows high CPU utilization. What’s the first command to use?
- show running-config
- show processes cpu
- show ip route
- debug all
Correct Answer: show processes cpu
Explanation: Displays which processes are using CPU cycles.
Practical Use: Identify stuck routing, logging, or traffic flooding.
Why Others Are Incorrect:
- Config and route views don’t show CPU.
- Debug all may worsen performance.
Objective: Device performance diagnostics
Follow-up: What command shows memory usage alongside CPU?
Q: What is a sign of a misconfigured QoS policy?
- Increased ping times
- Incorrect VLAN mapping
- Uneven packet priority
- Duplicate MACs
Correct Answer: Uneven packet priority
Explanation: Poorly applied QoS may drop or delay traffic inconsistently.
Practical Use: Recheck policy-map or class-map on interfaces.
Why Others Are Incorrect:
- VLAN and MAC errors are separate issues.
Objective: QoS issue recognition
Follow-up: What command shows service policy applied to an interface?
Q: Which command shows all NAT translations on a router?
- show ip nat translations
- show interfaces
- show running-config
- show vlan brief
Correct Answer: show ip nat translations
Explanation: Displays the NAT table with internal/external IP mappings.
Practical Use: Diagnoses NAT failures and IP overlap.
Why Others Are Incorrect:
- Other commands don’t show active NAT mappings.
Objective: NAT troubleshooting
Follow-up: What command shows NAT interfaces and ACLs?
Q: What symptom might indicate DHCP scope exhaustion?
- Users get duplicate IPs
- Users can’t renew leases
- Users get public IPs
- DNS stops resolving
Correct Answer: Users can’t renew leases
Explanation: DHCP cannot assign new IPs when the scope is exhausted.
Practical Use: Check pool size and lease duration.
Why Others Are Incorrect:
- Duplicates are often static config issues.
- DNS isn’t directly affected.
Objective: DHCP pool management
Follow-up: What command verifies active DHCP leases?
Q: How do you measure network latency?
- nslookup
- show interfaces
- ping
- ipconfig
Correct Answer: ping
Explanation: Measures round-trip delay to a destination.
Practical Use: Baseline and compare over time.
Why Others Are Incorrect:
- Other tools do not measure delay.
Objective: Latency tracking
Follow-up: What tool shows latency per hop?
Q: Which term describes variation in packet arrival time?
- Latency
- Jitter
- Throughput
- Bandwidth
Correct Answer: Jitter
Explanation: Jitter is the inconsistency in packet delay, harmful to real-time services.
Practical Use: Measure with tools like ping -t or specialized jitter monitors.
Why Others Are Incorrect:
- Latency = delay
- Throughput = transfer rate
- Bandwidth = capacity
Objective: Performance metric comprehension
Follow-up: What application type is most sensitive to jitter?
Q: What does NAT allow internal devices to do?
- Route VLANs internally
- Assign IPs to others
- Share a public IP for external access
- Discover hostnames
Correct Answer: Share a public IP for external access
Explanation: NAT enables many private IPs to use one public address.
Practical Use: Critical for IPv4 networks accessing the internet.
Why Others Are Incorrect:
- Not about VLANs or DNS.
- Doesn’t assign IPs.
Objective: NAT purpose
Follow-up: What is the NAT type that uses one-to-one mapping?
Q: Which protocol commonly causes high CPU load on misconfigured routers?
- FTP
- EIGRP
- SNMP
- STP
Correct Answer: SNMP
Explanation: Misconfigured SNMP traps or polling can overwhelm a device.
Practical Use: Check community strings and polling frequency.
Why Others Are Incorrect:
- Other protocols don’t trigger excessive logging or polling.
Objective: Performance impact analysis
Follow-up: What command disables SNMP on Cisco routers?
Q: What does ‘throughput’ measure?
- Available bandwidth
- CPU usage
- Actual data transfer rate
- Jitter over time
Correct Answer: Actual data transfer rate
Explanation: Throughput is the volume of data moved successfully across the network.
Practical Use: Measure with tools like iPerf or SNMP monitoring.
Why Others Are Incorrect:
- Bandwidth is capacity, not usage.
- CPU and jitter are unrelated.
Objective: Throughput comprehension
Follow-up: What tool tests throughput between two endpoints?
