What do employers exactly expect when they ask you knowledge of DHCP, TCP/IP, DNS?

Fayz

I was asked if I know about these 3 things. I know about these things theoretically like what they do and how it works. I have not worked with these things hands on enough. With TCP/IP the only thing I worked with directly was altering info on an IPv4 network connection like IP Address and DNS. I only installed DHCP and DNS roles in Windows Server 2012. How should I be practicing for these things to get better perspective on what to expect in a work environment.

Mike7

Guess they are asking from a trouble-shooting perspective.

Say a PC is unable to access internal file server share or go to internet. Are you able to find out why?
DHCP not assigning IP? PC configured with wrong IP subnet, gateway and/or DNS servers? DNS server not resolving queries?
How do you go about resolving? What do you look at first? What commands do you use to troubleshoot?

EnderWiggin

It depends on the job. If it's a tier one help desk position, they're probably just looking for you to know the definitions. If it's a systems administrator position, they may be looking for more in-depth knowledge, and hands-on experience.

dmoore44

From an InfoSec standpoint, how might the logs from those services be useful during an investigation? How might those logs be useful when you're writing detections or hunting for active infections? How might those services be abused?

cyberguypr

One question I have used to gauge networking understanding of desktop support personnel was "tell me what happens from a networking perspective when you boot up a computer". Another one was "describe in detail what happens when I type "xyz.com" in the address bar and hit enter. I also used a scenario where some users can get network connectivity and others can't. I purposely give vague information in order to see if the candidate would ask the right questions to get to the root of the problem.

OctalDump

cyberguypr wrote: »

One question I have used to gauge networking understanding of desktop support personnel was "tell me what happens from a networking perspective when you boot up a computer". Another one was "describe in detail what happens when I type "xyz.com" in the address bar and hit enter. I also used a scenario where some users can get network connectivity and others can't. I purposely give vague information in order to see if the candidate would ask the right questions to get to the root of the problem.

Yes, these are the kinds of questions to expect... if they are trying to interview you properly. They're a better way to get at the kind of knowledge you need to do the job you are being hired for, and will vary from position to position. It will (hopefully) be rare that they ask "Tell me about TCP/IP". If they do, then you are probably better to get them to clarify or narrow the scope of the question.

Especially in an interview situation, try not to make any assumptions from lack of information, you are much better to ask clarifying questions. As cyberguypr says, it's also the questions you ask that reveal your knowledge and thinking process, not just your answers. One thing you soon learn in IT is that the answer often depends on a lot of factors.

UncleB

A more common type of question I have been asked at interview stage is to see if you understand how these components work together to provide normal domain connectivity and how it to troubleshoot the common faults - for example I would be given the scenario:

A customer calls you and says they get a message that they cannot login - you check they are using the right login name and domain but the message is "There are currently no logon servers available" - what has probably gone wrong and how do you start fixing it?

Here you need to understand that the computer the customer is using is unable to connect to a domain controller to authenticate the logon credentials and you need to work through the most obvious stuff in order:
1 - is it even plugged into a network cable
2 - is the cable patched to the switch
3 - is the switch connection live (test with another computer connected to the same cable)
4 - does the computer have a static IP address - if so is it patched to a network on the correct subnet
5 - if it is DHCP assigned, try releasing/renewing the IP address (more of a bug with windows) - also check subnet mask and gateway details are correct.
6 - if that doesn't pick up a DHCP address, check the DHCP server is working (test another computer or login to server and check console for capacity & errors)
7 - if you get a DHCP address, can you lookup the login server name using nslookup (ie is the DNS working)

These should exhaust what I would expect from a 2nd line support engineers knowledge of basic DHCP troubleshooting (from a hiring managers perspective).

thanks
Iain

Kreken

As others said, it depends on the position. For helpdesk, it would be enough to say it is used for dynamic address assignment. For engineering position, it would require a bit more protocol knowledge and that it can be used for more than just IP assignments. That it is a replacement for BOOTP and etc.