Network Engineer Interview Questions

xenodamus

I thought some of you might find this list interesting. I work in a NOC that supports an international network and these are the interview questions that our manager picks from when he does interviews. Enjoy

General -
-Describe whether you are a network admin or server admin?
-Are you currently or have you worked as a member of a team? If yes, name some of the challenges and how you handled them. Are you currently or have you worked as a member of a team? If yes, name some of the challenges and how you handled them.
-Do you prefer routing or switching?
-What are your strengths and weaknesses?
-How do you troubleshoot network slowness issues?


Switching -
-On a Cisco switch, when would you use a "ip default-gateway" command, and when a default route ip route 0.0.0.0 0.0.0.0 x.x.x.x
-You create an SVI on 3560 switch, and its IP does not respond to ping. What could be the problem?
-On 3560 switch -What command would you use to view the mac table?
-On 6500 switch(IOS) - What command would you use to view the mac table?
-On 6500 switch(CATOS) - What command would you use to view the mac table?
-On Foundry(FOS) - What command would you use to view the mac table?
-What is the Native Vlan?
-3750 Switch-stack: which switch's flash holds the image that will run in
RAM when the stack is powered-up?
-What commands would you use to set up a trunk between 2 cisco switches
-What commands would you use to set up a trunk between 1 cisco switch and 1 cisco router
-Difference between BPDUGUARD/BPDUFILTER
-Explain how STP works
-What is spanning tree protocol and how does it work?
-Difference between a trunk and an access layer switch port?
-Two PCs attached to 2 different switches. The switches are connected to each other but the PCs can't ping each other. Possible reasons? Steps to troubleshoot?
-Link status is up, but line protocol is down - what's wrong?
-You have a switch that won't power on. How do you get it replaced?
-Describe how multiple VLANs can exist on a single switch link
-Name a trunking protocol you have used and how it works (

Routing -
-OsPF- configuration statement
-HSRP - what is "interface tracking" used for ?
-Which has a higher admin distance- EBGP(20) or EIGRP(90)
-Which has a better admin distance- EBGP or EIGRP
-BGP- When would you apply a Weight to a BGP neighbor?
-BGP- When would you prepend an AS path?
-BGP- If you prepend a prefix's AS Path, does the prefix look better or worse to the world?
-BGP- What command would you use to see your BGP neighbors?
-BGP- Who controls routing with an AS?
-EIGRP-Do Juniper routers run EIGRP?
-EIGRP- What is the difference between the EIGRP topology table, and the routing table
-EIGRP- In a network with dual redundant paths, how could you use an offset list
-What is the (TCP) 3-way handshake?
-How do you set up an OSPF network?
-You want to add an attached network into your OSPF configuration. What are the command(s)?
-What is redistribution in terms of routing protocols? What is mutual redistribution?
-What would be some problems with mutual redistribution?
-The LEC can't loop the CSU or NIU on a T1 circuit. Should you get the Cisco WIC replaced?

OSI Model
-In OSI terms, briefly describe what happens when you enter "www.google.com" in your
browser address bar, and hit enter
-Name the 7 layers
-What layer is TCP?
-What layer does a proxy server operate at?
-Describe the process by which one layer communicates with the next

Subnetting
-Usable hosts in a /23?
-How many bits for hosts are there in a /27?
-What's the dotted decimal equivalent of a /28?


DNS
-How do you look up a MX record?
-What is a CNAME?
-What is an A record?

Other
-How can you view routing information in a Unix server?
-How can you configure a static route in a Unix server?
-What is the command to list your current directory in Unix?
-Give an example of a regular expression used with the "|" character, in Cisco, or Unix
-Trick question--If you change the "bandwidth" on a router interface, and the interface utilization drops,
what could be an explanation?
-Have you used Wireshark?
-If I give you a Ethernet cable and pair of scissors can you make me a DS-1 loop back plug ....?
-Stateful firewall vs. access-lists vs. proxy server - how are they different?
-How do you show the arp table on a linux box? On a windows box? On a Cisco router?
-Briefly explain the difference between static and dynamic NAT
-Briefly explain the use of a virtual IP address in HSRP or VRRP

hiddenknight821

xenodamus wrote: »

-If I give you a Ethernet cable and pair of scissors can you make me a DS-1 loop back plug ....?

I dunno whether to laugh or not, but personally I think this is funny.

I'm definitely gonna fail the interview if I'm sitting in one right now. Don't some of the questions automatically wavied other questions since you can't know one thing without knowing the prerequisite knowledge?

pham0329

-Describe whether you are a network admin or server admin?

hmmm...is there a right answer here? What if I think of myself as both?

Link status is up, but line protocol is down - what's wrong?

Can this even happen on a switch if it's a L2 port?

networker050184

These are your engineer level questions? The vast majority of these seem pretty low level. Seems more like something you'd ask a NOC Tech to me.

ColbyG

networker050184 wrote: »

These are your engineer level questions? The vast majority of these seem pretty low level. Seems more like something you'd ask a NOC Tech to me.

You're all spoiled now, lol. I could ask some of these to a lot of engineers in this area and they'd look at me cross-eyed and fall over.

xenodamus

networker050184 wrote: »

These are your engineer level questions? The vast majority of these seem pretty low level. Seems more like something you'd ask a NOC Tech to me.

Yep, that's for the engineers. I'm a Jr. Engineer and my interview only consisted of the 5 easiest questions you could pull from that list. Things like:

- What's the difference between a collision and broadcast domain?
- How do you configure a trunk on a switch?
- How do you configure RIP?

I'm glad I didn't get any of the more...interesting...questions up there.

shodown

networker050184 wrote: »

These are your engineer level questions? The vast majority of these seem pretty low level. Seems more like something you'd ask a NOC Tech to me.

I thought the same thing that I would blow right through these and I'm a VOIP engineer

networker050184

ColbyG wrote: »

You're all spoiled now, lol. I could ask some of these to a lot of engineers in this area and they'd look at me cross-eyed and fall over.

Some of them are pretty good, but what command would you use to see your BGP neighbors? Yeah, if you need to even ask your engineer that you shouldn't be thinking about hiring them.....

JohnnyBiggles

Could we get some clear-cut answers on these just to have? I know most of these I'm just saying it may help out as quick reference

hiddenknight821

JohnnyBiggles wrote: »

Could we get some clear-cut answers on these just to have? I know most of these I'm just saying it may help out as quick reference

Haha, I'm glad you finally asked. How long did you wait to get an answer? I'm looking forward to see if they have the answer to the one I picked out. Don't worry. I'm just as clueless as you are on some of the questions. I believe you should know the answer to at least 25% of the questions above if you have a CCNA.

Mishra

I'm a systems engineer that makes sure to be able to keep up on networking/Cisco at least a little bit. I decided to try and answer the question for the fun of it. I've never been in charge of a piece of networking equipment.




Switching -
-On a Cisco switch, when would you use a "ip default-gateway" command, and when a default route ip route 0.0.0.0 0.0.0.0 x.x.x.x

To set a gateway?

-You create an SVI on 3560 switch, and its IP does not respond to ping. What could be the problem?

Don't think I know what SVI is.

-On 3560 switch -What command would you use to view the mac table?

Show mac-address table

-On 6500 switch(IOS) - What command would you use to view the mac table?

Same thing?

-On 6500 switch(CATOS) - What command would you use to view the mac table?

Never studied CATOS

-On Foundry(FOS) - What command would you use to view the mac table?

Never studied Foundry

-What is the Native Vlan?

Vlan 1

-3750 Switch-stack: which switch's flash holds the image that will run in
RAM when the stack is powered-up?

NVRAM

-What commands would you use to set up a trunk between 2 cisco switches

Something like switchport-access-trunk

-What commands would you use to set up a trunk between 1 cisco switch and 1 cisco router

You can't trunk a router?

-Difference between BPDUGUARD/BPDUFILTER

I think I used to know this but don't anymore.

-Explain how STP works

Spanning-Tree blocks switch loops.

-What is spanning tree protocol and how does it work?

STP. I know terms in STP like root bridges and convergence but couldn't explain it in depth.

-Difference between a trunk and an access layer switch port?

Trunking is between switches and shares vlans. Access layer is the end device.

-Two PCs attached to 2 different switches. The switches are connected to each other but the PCs can't ping each other. Possible reasons? Steps to troubleshoot?

Speed mismatch/Phyiscal layer issues/VLAN issues/could go on.

-Link status is up, but line protocol is down - what's wrong?

Layer 2 issue. Things like speed mismatches.

-You have a switch that won't power on. How do you get it replaced?

Call Cisco? lol If you are talking about how do you put in the replacement, then just move the configuration. Hopefully you have backups.

-Describe how multiple VLANs can exist on a single switch link

Trunking?

-Name a trunking protocol you have used and how it works (

802.1q . No idea how it works.

Routing -
-OsPF- configuration statement

network, areas, AS. About the only configuration spewing I could do.

-HSRP - what is "interface tracking" used for ?

HSRP is used for HA. That's all I know.

-Which has a higher admin distance- EBGP(20) or EIGRP(90)

I'm pretty sure lower numbers are better.

-Which has a better admin distance- EBGP or EIGRP

EBGP?

-BGP- When would you apply a Weight to a BGP neighbor?

Never studied BGP.

-BGP- When would you prepend an AS path?
-BGP- If you prepend a prefix's AS Path, does the prefix look better or worse to the world?
-BGP- What command would you use to see your BGP neighbors?
-BGP- Who controls routing with an AS?
-EIGRP-Do Juniper routers run EIGRP?

No.

-EIGRP- What is the difference between the EIGRP topology table, and the routing table

I think toplogy table shows you router distances. Routing is obvious.

-EIGRP- In a network with dual redundant paths, how could you use an offset list

No idea

-What is the (TCP) 3-way handshake?

Ack, fin, syn

-How do you set up an OSPF network?

? Commands or in general?

-You want to add an attached network into your OSPF configuration. What are the command(s)?

network IP subnet

-What is redistribution in terms of routing protocols? What is mutual redistribution?

Dunno.
-What would be some problems with mutual redistribution?
-The LEC can't loop the CSU or NIU on a T1 circuit. Should you get the Cisco WIC replaced?

OSI Model
-In OSI terms, briefly describe what happens when you enter "www.google.com" in your
browser address bar, and hit enter

I could get really detailed with this...

Layer 7 DNS request. Layer 3 routing. Layer 7 HTTP communication.

-Name the 7 layers

Physical, Data, Network, Transport, Session, Presentation, Application

-What layer is TCP?

4

-What layer does a proxy server operate at?

7

-Describe the process by which one layer communicates with the next

Not typing.

Subnetting
-Usable hosts in a /23?

1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 + 256 - 1
-How many bits for hosts are there in a /27?

6

-What's the dotted decimal equivalent of a /28?

11111111.11111111.11111111.11100000

DNS
-How do you look up a MX record?

nslookup; set type=mx
-What is a CNAME?

Maps a name to a name

-What is an A record?

maps a name to an IP

EASY SECTION!!!!

Other
-How can you view routing information in a Unix server?

netstat -rnv

-How can you configure a static route in a Unix server?

route add IP mask MASK

-What is the command to list your current directory in Unix?

ls

-Give an example of a regular expression used with the "|" character, in Cisco, or Unix

cat file | grep hello

-Trick question--If you change the "bandwidth" on a router interface, and the interface utilization drops,
what could be an explanation?

QOS is configured wrong?

-Have you used Wireshark?

Yes

-If I give you a Ethernet cable and pair of scissors can you make me a DS-1 loop back plug ....?

I've made a T1 cable before but would have to look it up.

-Stateful firewall vs. access-lists vs. proxy server - how are they different?

Firewalls can search more indepth in the data, access-lists are a pure Layer 2-4 blocking mechanism, proxy just masks.

-How do you show the arp table on a linux box? On a windows box? On a Cisco router?

Windows, arp -a
Linux, Same command I think...
Cisco, show mac-address table (right?)

-Briefly explain the difference between static and dynamic NAT

Hmm... don't think I can but I feel like I should be able to.

-Briefly explain the use of a virtual IP address in HSRP or VRRP

It's the load balancing IP.

whatthehell

Great post! +1 for you!

Hypntick

xenodamus wrote: »

-How do you troubleshoot network slowness issues?

Blame the servers...

Devilry

great post!

+1 for you