Network Support Interview questions

The following interview questions are based on typical scenarios encountered in a network support environment.

Interview question 1

In the below topology, a router is setup for internet sharing. The TCP/IP adapter setting on the computers are presently configured with the respective IP address and subnet masks. The DNS server provided by the ISP is configured on the router. The LAN IP address of the router is 192.168.1.1. Identify the required additional parameters which needs to be configured on the TCP/IP adapter of the PC’s from the below options.

A. Default gateway and DNS servers as 192.168.1.1
B. Default gateway as 192.168.1.1, DNS server not required.
C. Default gateway as the IP address of the switch, DNS server not required
D. Default gateway as the DNS server of the ISP.

Explanation

DNS servers are required for computers to access internet. DNS servers are responsible for resolving URL into IP address which is mandatory for network communication. The computers which require access to the internet needs to be configured with the respective DNS server IP address. The default gateway also needs to be configured as internet bound packets resides on different networks. In the above topology, the internet provided DNS server IP address is configured on the router. This implies that the router is aware of whom to contact for name resolutions.
The DNS server IP addresses for the respective computers are configured with the routers IP address. When the a user on the computer types a website name, a DNS request packet is generated for identifying the IP address of the URL corresponding to the website name. This packet is sent to the router from where the, DNS request packet is sent to the ISP provided DNS server. The gateway address for the computers needs to be configured with the LAN IP address of the router, 192.168.1.1.

Answer – A

Interview question 2.

Users on a network are unable to access the internet. Name three steps which you would use to troubleshoot the issue.

a. Check if the router is configured and setup with a public IP address and appropriate DNS servers.
b. Check the TCP/IP adapter settings of the users for DNS server IP address.
3. Check if appropriate routing is enabled on the router.

Interview question 3.

On a network, users are unable to receive an IP address from the DHCP server on the network. Name the steps you would follow to troubleshoot the issue.

a. Check if the DHCP Server is reachable by ping.
b. Check if the DHCP service is up and running on the system.
c. Check if the DHCP servers and clients are on the same network.

Interview question 4.

You are a network support engineer who has been asked to setup internet sharing for users on the network. The type of traffic for which internet is required is HTTP, FTP, Telnet ICMP etc. Which technology would you use (Proxy Server or NAT) and why ?

Different types of protocols require access to the internet. A proxy server is specific on the type of application or protocol for which internet access is required. This would not suffice the purpose. So a NAT router would be required.

Interview question 5.

What tool would you use to check if a remote port is open or closed ?

nmap can be used for the purpose.

Interview question 6.

Which protocol would you use to remotely manage a router and why ?

SSH , because it is secure.

Interview question 7

Name one practical scenario where you would use port forwarding feature on a router ?

In a situation , where a PC on the LAN network requires access from the outside network like the internet. The PC can be configured for remote desktop connection and appropriate port forwarding configuration can be setup on the router.

Interview question 8

Does the DNS server and default gateway be the same address ?

It need not be. If it is the same, the actual DNS server address is to be configured on the gateway.

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