Help Desk interview -could not solve DHCP problem

Meditator

I had third (technical) phone interview yesterday, was told that there wasn't gonna be anything technical since I already went through 1st technical (initial) interview and 2nd multiple choices test- but was completely surprised by it. Almost at the end, I was ask to remote in and to solve Network connectivity ( now I know why I was asked to have PC available in front of me).

Anyway, the problem seemed simple enough for me since I have done it before- 'user can not get on internet'. At the command page, I ran a ping to see if there was problem by pinging, say, yahoo.com- no go. Then, I checked my Network card by pinging 127.0.0.1 and that was ok. Then I ran "ipconfig /all" and noticed that DHCP was not enabled, so went to Control Panel, Network/Internet > Network stat, TCP/IP v4 > properties. At the Properties page, I noticed that DHCP was set on private address, so I clicked on at Auto DHCP. Went back to CMD page and still no IP address assigned for me, so obviously couldn't ping anybody except myself .

I was at that page for about 5mins and so still couldn't figure it out. I asked the the interviewer if there was any other solution. He mentioned if I could think of something about server. Anyway the interview is now over, and I am really curious to what will be the possible solution for this. Looking at the server from CMD page or from PC- is that even possible. I mean I could try to telnet/ SSH to Switch and see if the interface was up- but wasn't sure if I had that option to do it. I wasn't told what the problem was or what the solution could have been.

swisschris104

ipconfig /release
ipconfig /renew

Thats the other thing that I would do but idk much about servers. Unless u go onto server and set Role of DHCP. idk

Asif Dasl

You say you couldn't ping Yahoo.com but could you have pinged 8.8.8.8 ? - If you could then it would have been a DNS issue and if you set the primary DNS to 8.8.8.8 you might have been able to ping Yahoo.com then. Maybe they had a proxy server and you just needed to tick the box in IE?

What I don't get is if you didn't have Internet connectivity on the machine you were repairing then how did you do it remotely?

Meditator

ipconfig /release
ipconfig /renew

Already tried those too! Also, did the DNS enabled also -on the same page as TCP/IP prop.

The remote service I was tested on, was a simulation program- I think, since I had to remote in to their website.

spicy ahi

On the server? Maybe they had the machine in the wrong DHCP scope and it was getting bad DNS IP's or something? I haven't played with servers in a while but I recall having an issue like that and scope came to mind while I was reading your scenario...

Qord

Could have been no dhcp server at all, there could have been one that was out of addresses, the service could have stopped...there are many reasons it could have failed, but those are the first to come to mind.

ajs1976

what IP was it set to? You mentioned Private. Do you mean a 10, 172, or 192 address? Why would you turn DHCP on. Maybe the computer had a hard coded IP.

What DNS addresses were used and did they look correct?

kurosaki00

did you remote to a server or a pc?
Because if a server... you can troubleshoot a lot of stuff

PC wise... Id say, maybe check if internet adapter was enabled (ethernet + wireless)
Why do you say its a DHCP problem when you're not getting the default data (default gateway, IP, DNS)
Did you had a default gateway? could you ping to it?

PS. Did you checked if you had an IP previously before starting to troubleshoot?
was it maybe 169. . . ?

VAHokie56

I think it depends on the level he wanted you to trouble shoot , if the box had a static address there is no telling how the internal routing of the network **** to the internet...I would of done a trace route to see where I died trying to get to the web and then looked at that router/switch for a default route...but really even that could go into a whole other portion of trouble shooting security domains and blah blah blah. If you changed it to dhcp and got a 169. a good question to ask would of been is the switch port associated with a vlan that has a dhcp helper address on it ? I think he just wanted to see how you would approach the issue and what questions you would ask...from I can tell not an issue with the box but rather the dhcp server or internal routing to the internet. My 2 cents

Xyro

VAHokie56 wrote: »

I would of done a trace route to see where I died trying to get to the web...

Same, but I thought I was way off since no one else was mentioning it haha.

VAHokie56 wrote: »

I think he just wanted to see how you would approach the issue...

Yes, definitely... that is why he gave Meditator the theoretical "answer". It's where he would have liked to see him arrive.

About7Narwhal

kurosaki00 wrote: »

PS. Did you checked if you had an IP previously before starting to troubleshoot?
was it maybe 169. . . ?

I too am curious if this was an apipa problem. But I also agree that their might have been no possible solution depending on how much information you had at the time. Who knows ??

rsutton

It's a process of elimination game, and the person interviewing you wants to know if you can eliminate the right things, in a logical order. You should start with what you know, and then troubleshoot accordingly.

I usually start with an ipconfig/all to check my IP and DNS. If my IP is good I will try to ping an external host name, and an external IP. Depending on the outcome, I will check if I can ping my gateway. These initial tests isolate all kinds of potential issues, and your left with a smaller list of potential problems to troubleshoot.

Xyro

The first issue I notice here is you pinging yahoo.com. That's great but if you only pinged by domain & not by IP ... then abandoned it to continue troubleshooting something else... you then create a "fork" in the troubleshooting "road" because you never checked to see if the problem was caused by DNS or not.

Just my 1 cent. I don't believe I've even earned 2 cents yet

Meditator

Reason I chose to ping "yahoo.com"-it could have been any website, before anything else was to make sure that there even was a problem getting on Internet at all. From my experience, if someone said there's a problem in something doesn't mean it is- easier to verify anyway.

After, "ipconfig /all" that's when I noticed I didn't even have IP address of anykind which lead me to believe DHCP (server) not handing out IP address. No APIPA "169.254.xx.xx either. After enabling DHCP (and DNS), still no IP address or default gateway. Release and Renew commands didn't help either. Of course, I was suggested to check the server. But, I am not real sure how from PC command page, not that I would know what to do at the server anyway.

sheckler

I see we live in the same city, I'm applying for support jobs also so now I'm wondering if I'm going to get this same interview.

Qord

Meditator wrote: »

No APIPA "169.254.xx.xx either.

Normally that would point to a nic problem if it's set to dhcp, but being able to ping 127 makes it seem like the nic is fine. Odd.

CodeBlox

I would have checked to see if a DHCP server actually existed. If it did I would then ask to confirm whether or not it's on the same subnet (Which it might not be) and if it isn't, I'd ask to confirm that helper addresses are setup. I'd then verify that a scope exist for my subnet. Thats where I'd have started as others have stated.

Xyro

Yes, pinging "yahoo.com" was a good idea, IMO; however, I wouldn't have branched off to troubleshoot other items yet until I also pinged it by IP address. Everyone has their own troubleshooting styles apparently. I just wouldn't have moved on without confirming whether or not it was a DNS issue or not.

it_consultant

The solution may have been impossible, but I can see some issues with your troubleshooting. If you noticed it was set to a private address then you always start pinging the default gateway because if you can't get to the default gateway, no way you can make it to yahoo - by DNS or by IP. If you had the private address in the NIC config but it didn't show up in the 'ipconfig' then we are looking at basic things like is it plugged in, did you disable and re-enable the NIC card, is the private IP configured on the correct interface etc.

Now that I think of it, I am almost sure the problem was probably DNS. They probably wanted you to enter a known good DNS server. They already provided you a private IP address, had you pinged the DG and found it responsive, you would know the network layer was OK. Then it is name translation. Remember 4 ip addresses for the rest of your life, 8.8.8.8, 8.8.4.4, 4.2.2.2, and 4.2.2.1. Those the most common public DNS servers. If you couldn't "get to the internet" but you could ping your router and one of those IPs, local DNS is the most likely culprit.

jsb515

I would have done the same basic things like pinging, loop test, ect.. but that private address that was hard coded could have had a network address instead of a host address for the ip or possible incorrect subnet. I would also have done a tracecert and make sure the gateway was set correctly and look to see where the fails happen.

But hunch tells me the ip address was incorrect and could have been a test on your subnetting skills..

Meditator

"I see we live in the same city, I'm applying for support jobs also so now I'm wondering if I'm going to get this same interview. "

No, it's not in Florida. Job market here is horrible! Almost across the country, probably have to move " if" I get the job offer.

As mentioned before, I didn't see IP address assigned to this PC or default gateway neither in the ipconfig /all page, which was the very 1st thing I looked for - from studying my CCNA (MAC is for L2, and IP is L3- no IP no Internet). When I troubleshoot problem like this at my other Help Desk job, and as mentioned by others, I always, always ping Default gateway. The fact that there was no IP address or subnet mask not to mention the IP address for DNS or Default gateway-led me to believe that nothing was giving this PC an IP address. If I couldn't ping outside and there was IP address there, I may have looked to see if they were in the same subnet or even to check on DNS.

Here's the strange thing, even after clicking on DHCP enabled (along w/ DNS) on TCP/IP property page, DHCP enabled and DNS enabled still showed "NO" -looking at command page through ipconfig /all. After these steps, the interviewer mentioned to me that I may need to check on the server.

jsb515

was the patch cable plugged in? lol that is so common to. I remember one of my instructors had us troubleshooting a pc issue and the whole time he had the ethernet unplugged and he said "First lesson always check your cabling, it will save you a lot of time" and I've never forgotten that and have actually ran into that a lot in the work field.

Meditator

No, this was "remote" session (simulation) -remember? There was no way I could check the cable. Checking the cable-physical level was the first thing I told the interviewer I would be doing, then all the "ipconfig /all" , "pings" we have been discussing.

NotHackingYou

Next time try pinging something external by name an by IP address. If you wearn't getting an IP, that's an issue in and of itself. Were you allowed to ask if they used DHCP or a static scheme? Could you ask if the network cable is plugged in and the light is on?

Also you could try netstat -rn to see the Windows routing table (this would be useful after you had an IP) in case they set up a static route to nowhere for all traffic.

Assuming you checked for the network card being enabled and no driver issue in device manager, ect.

Psoasman

Not much to add for troubleshooting here Keep in mind that they also want to see how you may react in a situation like that.

Xyro

You were caught off-guard & you did the best you could. That's what matters here.

One can do no better than their best. Good luck in getting the job.

dt3k

I'm not sure of the setup they used, but if they gave you an IP address of a computer to remote into over the internet, then wouldn't it of had internet connectivity? This would indicate a DNS problem if you could reach it via IP over the internet but it could not ping yahoo. Did you remote into a different system and they pulled up a VM or something?

W Stewart

From the hints the interviewer gave you it's obvious the computer wasn't getting an IP from a dhcp server but what steps you should have taken would depend on what the simulator would even allow you to do. The simulator may have wanted you to log into a simulated dhcp server or a simulated router which would be acting as a dhcp server and verify the configuration. It may have even wanted you to make sure the simulated cables were connected but again that would completely depend on what kind of simulator it is. If it didn't have an ip address then there's an issue somewhere between that pc and the dhcp server. They may have even wanted you to set a static ip address. We would really need more info to tell you what could have been done. Also some simulators are just plain broken and don't operate as expected especially if you're using an unsupported browser. I really would have asked the interviewer what dhcp server he was referring to if it wasn't obvious on the simulator or didn't have instructions since they can't expect you to know where all of their network devices are.


Edit: Another thing that doesn't make any sense is that if it was set to dhcp but it wasn't getting an address then it should have defaulted to a 169.254.x.x address but it could just be a case of an inaccurate simulator.

TeKniques

The DHCP server probably did not have an authorized scope (since he hinted to the server). Everything else you did seems right to me.

Tooms

Without knowing all the details its hard to tell. Router could be missing a helper address for all we know.

it_consultant

I wouldn't feel too bad - I biffed an easy lab about a year ago. I couldn't get the Lab Exchange server's info store to mount. I googled it, examined the logs, scratched my head...by the time I realized the drive holding the store was completely full...it was too late.