Network Troubleshooting Interview questions

The network troubleshooting interview questions are a sample from the below 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

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 3

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 ?

The switch will not retain the mac-address. When the port is shutdown, the mac- address would be removed from the mac-address table of the switch.

Question 4

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 5

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.

Port forwarding feature can be used to achieve the functionality. Port forwarding feature can be configured on the router to forward all requests to TCP port 20 and 21 which are used by FTP servers to the appropriate LAN IP address of the FTP server. Users can then FTP into the public IP address of the router which is connected to the internet. When the router receives the request, it forwards to the internal FTP server IP address.

Question 6

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 7

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

When a user on a PC accesses a website, URL resolution for the website name has to be performed. This is done by the DNS protocol. This request has to be sent to a DNS server, for which the IP address of the DNS server should be configured on the client.