Common Networking Interview Questions

Network administration is a complex field that requires an immense amount studying and dedication. Below are ten common entry-level interview questions. Now I must add that you should not memorize these questions, but instead should use them as a basis for your level of understanding. (Questions 5 through 7 may very depending on the job, but this is the general layout.)

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1. What is an IP address? An IP address is a logical address mapped to a MAC address that then helps to identify a computer across a network.
2. What is DNS? DNS, which stands for Domain Name Service, is the act of converting URL names into IP addresses.
3. What is the main difference between POP3 and IMAP? Both of these are responsible for the delivery of emails, however POP3 does not update the central mail server whenever an email has been read or deleted. IMAP on the other hand directly updates the server.
4. What is a VLAN? A VLAN, which stands for Virtual Local Area Network, is directly correlated to the size of the broadcast domain, it provides connectivity for a subnet. This is great as it allows devices on different switches to be within the same domain.
5. You are trying to setup an IMAP and SMTP email account on a client's desktop, the ports 993 and 587 for TLS encryption do not work, however the defaults 143 and 25 do, what are the two things you check? The first thing I would check is the TLS/SSL encryption, if that is establishing correctly and the certification is valid, I would then check to see if the firewall is blocking any of the ports.
6. You have a network that has all statically assigned IP addresses, after connecting a computer to the network and assigning it, another desktop drops connectivity every few minutes. What is the issue? The issue is more than likely an IP address conflict, I would check the IP table on the router and assign the next available address to the computer.
7. You have a switch that randomly stops forwarding all traffic, what is your troubleshooting steps? First I would make sure that it has power, after power cycling, I would then check to make sure all of the ports allow traffic. If all of the ports allow traffic I would then check to make sure that the router is forwarding traffic. If I can isolate the issue to be with the switch, I would look into updating the firmware next.
8. What is the difference between TCP and UDP? The main difference is that TCP is connection-orientated, whereas UDP is connection-less.
9. What is the difference between a Domain and a Workgroup? The difference is how resources are allocated and sorted. A Workgroup is great for a small business or home environment, however falls short whenever it grows past 15 computers. Here, all computers act as peers, with each user requiring a local account on the computer, and all computers must be within the same network. Lastly, a Workgroup is not password protected, meaning that anyone can connect. A Domain on the other hand is a useful way of managing the permissions and security policies within a network as certain computers act as servers allowing for scalability. Here, a Domain can easily exceed over a hundred computers, however can be extremely complex to maintain and requires oversight.
10. What is a router? A router is device that connects networks together, it is responsible for forwarding the traffic in and out of a network.