ICND1 Troubleshooting 5 — Questions and Answers
Question 1: A technician finds that two Cisco switches are connected with a crossover cable but the link is down. What feature would resolve this automatically on modern Cisco switches?
- Port security
- Auto-MDIX (Correct answer)
- PortFast
- EtherChannel
Correct answer: Auto-MDIX
Auto-MDIX automatically detects and corrects the cable type needed, eliminating the need for crossover cables on modern Cisco switches.
Question 2: You run 'traceroute 8.8.8.8' from a router and the output shows asterisks (*) at every hop. What does this indicate?
- The destination is unreachable
- ICMP or UDP packets are being blocked by a firewall or the device doesn't send ICMP TTL exceeded messages (Correct answer)
- The route is looping
- DNS resolution failed
Correct answer: ICMP or UDP packets are being blocked by a firewall or the device doesn't send ICMP TTL exceeded messages
Asterisks in traceroute output mean no response was received within the timeout, usually because ICMP is filtered or the device doesn't respond.
Question 3: A host cannot ping its own default gateway. After checking the cable, what should be checked next on the host?
- The switch's MAC address table
- The host's IP address, subnet mask, and default gateway settings (Correct answer)
- The router's routing table
- The ARP table on the router
Correct answer: The host's IP address, subnet mask, and default gateway settings
Incorrect IP addressing on the host, such as a wrong subnet mask, can prevent communication even with directly connected devices.
Question 4: Which Cisco IOS command would you use to verify that DHCP is assigning addresses from the correct pool?
- show ip dhcp conflict
- show ip dhcp binding (Correct answer)
- show ip dhcp pool
- debug ip dhcp server events
Correct answer: show ip dhcp binding
'show ip dhcp binding' displays all current DHCP leases showing which IP addresses have been assigned to which MAC addresses.
Question 5: A router running EIGRP shows a neighbor in ACTIVE state for longer than 3 minutes. What does this condition indicate?
- The neighbor relationship is fully established
- The router is stuck in active (SIA) and will drop the neighbor (Correct answer)
- Traffic is passing normally through the neighbor
- EIGRP is recalculating routes normally
Correct answer: The router is stuck in active (SIA) and will drop the neighbor
Stuck-In-Active (SIA) occurs when a router doesn't receive a reply to a query within the active timer, causing it to drop that neighbor relationship.
Question 6: After configuring a new subinterface for router-on-a-stick, inter-VLAN routing still doesn't work. What is a likely misconfiguration?
- The physical interface has an IP address assigned
- The encapsulation dot1q VLAN ID on the subinterface doesn't match the switch trunk VLAN (Correct answer)
- The routing protocol is not configured
- The switch port is in access mode
Correct answer: The encapsulation dot1q VLAN ID on the subinterface doesn't match the switch trunk VLAN
The 802.1Q encapsulation VLAN ID on the router subinterface must match the corresponding VLAN on the switch trunk for proper tagging.
Question 7: You issue 'show ip interface brief' and notice an interface shows 'administratively down.' How do you bring it up?
- Reconnect the network cable
- Issue 'no shutdown' in interface configuration mode (Correct answer)
- Configure a valid IP address on the interface
- Reload the router
Correct answer: Issue 'no shutdown' in interface configuration mode
An 'administratively down' interface has been manually disabled with the 'shutdown' command and requires 'no shutdown' to re-enable it.
ICND1 Troubleshooting 5
A technician finds that two Cisco switches are connected with a crossover cable but the link is down.
What feature would resolve this automatically on modern Cisco switches?