Network Troubleshooting Interview questions

The network troubleshooting interview questions are a sample from the ebook – 250+ Network Engineer Interview questions and answers

Question 1

A computer is connected to the internet via an ADSL router. The ADSL router is configured with appropriate DNS server IP address. Is it required to configure the DNS server IP address on the computer as well for internet access.

It is required for the DNS server IP address to be configured on the computer. Take an example, where the user wishes to browse a website. When the user opens the browser and types the URL name of the website, a DNS resolution has to take place, for which the URL name has to be sent to a DNS server. The PC has to initiate the DNS request, for which the DNS server IP address has to be configured on the PC. If not configured, the DNS request would fail as the PC would be unaware of DNS server IP address and internet access would fail.

Question 2

A network consultant deploys a network with 2 ethernet switches interconnected to each other with two physical links. After deployment, the company administrator provided IP addresses to the clients ( 20 PC’s on swicth1 and 20 PC’s on switch 2 )but accidentally provides an incorrect default gateway (Non existent IP address) for the users. After some time the administrator observes that LED of 2 switches starts flashing and the link is broken. What is the root issue?

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Question 3

An administrator of an organization is unable to telnet to a router, which is 10 hops away from the admin PC. What tool can be used to identify the location where the connection is dropped.

The admin can use traceroute command line tool to the router and check the location where the packets are being dropped.

Question 4

A PC which is connected to switch port 23. The switch has learned the mac- address of the PC. The port is now shutdown. Will the switch retain the mac- address ?

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Question 5

Two PC’s, PC1 and PC2 are deployed on different vlan’s , vlan 3 and vlan 4 respectively on a layer 3 ethernet switch. Each of the vlans are configured with respective IP addresses. What should be the IP address of the default gateway of TCP/IP adapter setting of PC1 to communicate with VLAN 4.

PC1 should be configured with the IP address of VLAN 3. This would ensure that all packets to vlan 4 would be sent to the default gateway, where it would be forwarded to PC2, which is on VLAN 4.

Question 6

A user in the company network complains that he is unable to connect to a FTP server on the internet. The user attempts to connect to the internet FTP server through a network layer firewall. The FTP server and client use Active FTP protocol. What could be the possible issue?

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Question 7

How can a FTP server residing on a LAN network accessed from a PC on the internet. Assume that the LAN network has an internet connection using a router.

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Question 8

If a PC has two default gateways, which would be taken for routing the packets.Every route entry would have a metric.

If there are two default gateways, there would be two default entry. The entry which has a lower metric value would be taken by the packets.

Question 9

Is a DNS IP address mandatory to be configured on a PC for internet access.

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Question 10

A switch is configured for two vlan’s, vlan 2 and vlan 3. DHCP clients are configured on vlan 2 and the DHCP server is configured on vlan 3. ip helper address is configured as the dhcp server ip address for vlan 2. What would be the destination IP address of the DHCP Discover packets from the clients just before it crosses vlan 2?

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