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Anyone got any networking interview questions?

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Scarpozzi

Scarpozzi

Lifer
I've got an interview next week for a network analyst position... My problem is, I've never really done switch or router config. I've always done systems administration and have only configured the switch modules on a few Dell blade chassis (Dell 5316m)before.

I understand a lot about trunks, vlans, iSCSI needs (jumbo frames), duplex stuff.... I'm just looking for a list of common questions so they don't catch me off-guard. I'm sure there's going to be a learning curve either way. I'm making the assumption this job will be running Cisco hardware, but they could be on HP or something else....

Anyone got some good interview questions?
 
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L2:
spanning-tree (different modes & protocols)
VTP

L3:
Understand how different routing protocols work, and their characteristics (BGP - path vector, OSPF - link state)

Read through a CCNA exam book and that should cover all the essential basics.
If time is limited, you can just study against the job requirements.
 
Explain difference between interior and exterior routing protocols and give examples of each and how they operate.
Explain in detail the OSI model and each layer.
What is ICMP and what is it's purpose? Give 3 examples.
You have 5 seconds - how many bits is a 255.255.224.0 netmask and how many hosts in that network?
What is spanning-tree and explain it's operation. Also why would a client connected to a switch not get a DHCP address on startup even though it has link?
What is the common cause for OSPF neighbors to be stuck in a 2-way exchange state.
You bring up EIGRP and notice there is a 10.0.0.0/8 route in your routing table, why is it there and how do you get rid of it.
What is the number 1 and number 2 causes of slow LAN performance.
Have you ever fucked with the physical layer? If so please leave immediately. 😉
You have configured two switch ports on different switches to be trunk desirable and specified an encapsulation type, what reasons could cause the switchports to not become trunks?
What is proxy ARP.
Is it EVER a network problem?
 
Originally posted by: spidey07
Explain difference between interior and exterior routing protocols and give examples of each and how they operate.
Explain in detail the OSI model and each layer.
What is ICMP and what is it's purpose? Give 3 examples.
You have 5 seconds - how many bits is a 255.255.224.0 netmask and how many hosts in that network?
What is spanning-tree and explain it's operation. Also why would a client connected to a switch not get a DHCP address on startup even though it has link?
What is the common cause for OSPF neighbors to be stuck in a 2-way exchange state.
You bring up EIGRP and notice there is a 10.0.0.0/8 route in your routing table, why is it there and how do you get rid of it.
What is the number 1 and number 2 causes of slow LAN performance.
Have you ever fucked with the physical layer? If so please leave immediately. 😉
You have configured two switch ports on different switches to be trunk desirable and specified an encapsulation type, what reasons could cause the switchports to not become trunks?
What is proxy ARP.
Is it EVER a network problem?
Click to expand...

If this is for an entry-level LAN type position, some of these questions are too complex. And the 5 seconds thing is silly - that would probably take me longer than 5 seconds (not very long, but still) and I have a CCIE.

I like to ask people what the difference between a MAC table and an ARP table is - really shows if they understand layer 2 vs layer 3.
 
@Spidey07: good questions, I would like to have stuff like that on an interview

I had an interview last week and I got a bunch of questions about mpls vpn and traffic engineering. I also got a simple question about the ip packet (what is the ttl field and what is the purpose of the ttl). Finally I got a bunch of questions about ATM and QoS on ATM.

edit: I got the job 😉
 
Originally posted by: freegeeks
@Spidey07: good questions, I would like to have stuff like that on an interview

I had an interview last week and I got a bunch of questions about mpls vpn and traffic engineering. I also got a simple question about the ip packet (what is the ttl field and what is the purpose of the ttl). Finally I got a bunch of questions about ATM and QoS on ATM.
Click to expand...

Wow, I guess a few people are still using ATM even though it's obsolete. Never will you find a more complicated layer 2 network technology. I used to work at the company that invented ATM so it is near and dear to my heart. 🙂
 
Originally posted by: Pheran
Originally posted by: freegeeks
@Spidey07: good questions, I would like to have stuff like that on an interview

I had an interview last week and I got a bunch of questions about mpls vpn and traffic engineering. I also got a simple question about the ip packet (what is the ttl field and what is the purpose of the ttl). Finally I got a bunch of questions about ATM and QoS on ATM.
Click to expand...

Wow, I guess a few people are still using ATM even though it's obsolete. Never will you find a more complicated layer 2 network technology. I used to work at the company that invented ATM so it is near and dear to my heart. 🙂
Click to expand...

Lot's of of telco are still in the migration phase to ethernet/mpls so yes it's still used often.

I worked for a telco for 7 years and when I left in 2007, the migration to mpls was just started. I probably configured and troubleshooted 1000's of PVC in my 7 years there.
 
Another good one "what is a native vlan mismatch and what are the implications of it?" I tend to ask questions that tend to reveal if somebody knows what they're doing and has a working knowledge of it, meaning they've done it before. You don't have to get everything right but the answers will show a lot.
 
Originally posted by: spidey07
Another good one "what is a native vlan mismatch and what are the implications of it?" I tend to ask questions that tend to reveal if somebody knows what they're doing and has a working knowledge of it, meaning they've done it before. You don't have to get everything right but the answers will show a lot.
Click to expand...

implication: the link will not be working 😛
 
Originally posted by: freegeeks
Originally posted by: spidey07
Another good one "what is a native vlan mismatch and what are the implications of it?" I tend to ask questions that tend to reveal if somebody knows what they're doing and has a working knowledge of it, meaning they've done it before. You don't have to get everything right but the answers will show a lot.
Click to expand...

implication: the link will not be working 😛
Click to expand...

Not so. What you effectively have done is bridge the native vlan on one side with the native vlan of the other. All tagged vlans will works just fine.
 
Originally posted by: spidey07
Originally posted by: freegeeks
Originally posted by: spidey07
Another good one "what is a native vlan mismatch and what are the implications of it?" I tend to ask questions that tend to reveal if somebody knows what they're doing and has a working knowledge of it, meaning they've done it before. You don't have to get everything right but the answers will show a lot.
Click to expand...

implication: the link will not be working 😛
Click to expand...

Not so. What you effectively have done is bridge the native vlan on one side with the native vlan of the other. All tagged vlans will works just fine.
Click to expand...

strange, I remember reading that there will be no forwarding

Cisco Press

Remember that the native VLAN must match on both sides of the trunk link for 802.1Q; otherwise the link will not work. If there is a native VLAN mismatch, Spanning Tree Protocol (STP) places the port in a port VLAN ID (PVID) inconsistent state and will not forward on the link.
 
I like to walk down the resume, line by line ( "experience with xxxx technology") and ask specific questions about each one of them. I want them to suffer from fluffing their resume. If it's on the paper, it's fair game ... if it turns out to be fluff, you're out the door.

Before we start that, I ask them what is their weakest point listed, and discuss that from the standpoint of what they can do (or be willing to do on their own) to improve in that area.

While I believe it is important to cover the technical stuff, I tend to push more to find out how they approach problems, how they troubleshoot, and ask them to write a paragraph explaining something semi-technical, to get a feeling about their ability to document their efforts in clear language.

Training can fix technical ignorance; not everyone can troubleshoot effectively, and fewer still (especially "these days") are technical *AND* literate enough to communicate both verbally and in writing.

.02
 
Originally posted by: freegeeks

strange, I remember reading that there will be no forwarding

Cisco Press

Remember that the native VLAN must match on both sides of the trunk link for 802.1Q; otherwise the link will not work. If there is a native VLAN mismatch, Spanning Tree Protocol (STP) places the port in a port VLAN ID (PVID) inconsistent state and will not forward on the link.
Click to expand...

heh, now THAT depends on the switch and the IOS version. 🙂
 
Originally posted by: spidey07
Originally posted by: freegeeks

strange, I remember reading that there will be no forwarding

Cisco Press

Remember that the native VLAN must match on both sides of the trunk link for 802.1Q; otherwise the link will not work. If there is a native VLAN mismatch, Spanning Tree Protocol (STP) places the port in a port VLAN ID (PVID) inconsistent state and will not forward on the link.
Click to expand...

heh, now THAT depends on the switch and the IOS version. 🙂
Click to expand...

so the correct answer is, "depends" 🙂

I also had a question last week about the difference between a certain command on Sun Solaris and HP Unix. I just answered, I type man <command> at the command prompt if I need this kind of information. The guy asking the question looked at me and just said "well that is also a valid answer" 😀


 
Originally posted by: freegeeks
Originally posted by: spidey07
Originally posted by: freegeeks

strange, I remember reading that there will be no forwarding

Cisco Press

Remember that the native VLAN must match on both sides of the trunk link for 802.1Q; otherwise the link will not work. If there is a native VLAN mismatch, Spanning Tree Protocol (STP) places the port in a port VLAN ID (PVID) inconsistent state and will not forward on the link.
Click to expand...

heh, now THAT depends on the switch and the IOS version. 🙂
Click to expand...

so the correct answer is, "depends" 🙂

I also had a question last week about the difference between a certain command on Sun Solaris and HP Unix. I just answered, I type man <command> at the command prompt if I need this kind of information. The guy asking the question looked at me and just said "well that is also a valid answer" 😀
Click to expand...
hard to chastise someone who actually RTFMs 🙂

this is a pretty interesting thread for me since im going to school for networking tech. ive been helping the campus admin lately and he said for the last cisco course, which is routing and the WAN iirc, that he spends some time at the end of the semester helping out with resumes and interview skills
 
Thanks for all the replies guys. I had a coworker show me some switch configurations so I understand about half of the questions that have been posted...not sure I have a right answer, but at least I get the concepts down.

Keep the questions coming...if you want to provide any answers to the questions, it will save me time. 😀 I've been reading some of my 10 year old networking books and am realizing that a lot has changed since then. I may have to hit Barnes & Noble tonight to get a CCNA study guide if I don't find a free online guide.
 
Originally posted by: Scarpozzi
Thanks for all the replies guys. I had a coworker show me some switch configurations so I understand about half of the questions that have been posted...not sure I have a right answer, but at least I get the concepts down.

Keep the questions coming...if you want to provide any answers to the questions, it will save me time. 😀 I've been reading some of my 10 year old networking books and am realizing that a lot has changed since then. I may have to hit Barnes & Noble tonight to get a CCNA study guide if I don't find a free online guide.
Click to expand...

just know the big concepts. I doubt they will ask you how BGP works in detail but they will expect you to know that is a an EGP, path vector routing protocol.

The same applies for STP, OSPF, RIP, EIGRP, ARP and whatever acronym they will throw at you.
Know the OSI layer model because this is in my experience one of the favorite questions
Know subnetting

just know the key concepts

for what kind of position is this?
 
What's the difference between native and hybrid IOS as it applies to switches?
What is the "switchport" command used for?
How do you turn a switch port into a routed port and what's the difference?
What is autoqos?
What is a Voice VLAN?
Name some layer2 WAN protocols
 
Spidey,

Do you still see many switches with the CatOS or hybrid OS? I have 1 cat 6500 where I'm at now that is hybrid and saw one 4000 with CatOS but that's it in the last 2 years.
 
CatOS is officially dead as of about summer of 2008 - that's when native IOS had every feature that CatOS had, until then there were really nice things you could do with catos that you couldn't with native. There's still plenty out there because migrating to native can be a bit daunting if the configs are complex.
 
2009? 😕😕 lol... he could be a network administrator by now, not just entry-level. :awe:

For what it's worth, it may depend on level/responsibility. Things such as describing OSI and TCP/IP stacks make sense, as well as routing protocols. If I were a manager in an IT functional area, I would have a practical assessment (even just a GNS3 application) and get all recruits to troubleshoot an error. I would select people based on how well they did in the test. Anybody can read a good networking textbook and cite by rote networking principles, but applying it is another thing. Even if somebody had a CCNA or even a CCNP, I would get them to do the assessment.
 
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