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Network Engineer Interview Questions

Are you thinking about getting a job as a Network Engineer?  Are you considering leaving your present position and getting a new job at a new company?  Has it been a while since you’ve interviewed?   If you’ve answered yes to any of these questions then this is the post for you!  We’ve compiled a list of things you need to do to be prepared for on your next interview.  We’ve also compiled a list of some tips for making sure you ace that interview as well as a list of 20 Network Engineer Interview Questions.

Can you pass the test?

Check also our new eBook
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Tips for preparing for the Interview

  1. Study – Before you go to your interview, open the books up and give yourself a general review of networking.
  2. Update your Resume – Read your resume and update it.  The last thing you need when you are putting your best face forward is to have a resume that is full of grammatical errors.
  3. Watch out for Social Networks – Many employers are getting very smart and will search on your name.  Be sure if they find your facebook or myspace page there isn’t anything there that you wouldn’t want them to see.
  4. Google yourself – Search for yourself on Google and see what you find.  You would be amazed an what might pop up. Make sure nothing derogatory shows up.
  5. Get Certified – One of the best things to do to prove you know what your talking about is a certification.  This gives a new employer an easy way to understand your  knowledge level.

 

Preparing for Network Engineer Interview Questions

Make sure you prepare well on those technical subjects. Don’t think that you know them already, actually spend time refreshing your knowledge to be and look more confident:

  1. IP Addressing- Make sure you know subnetting (without a subnet calculator!).  Know the value of every bit in each each Octet. Know subnet masks and what their slashed notation is and CIDR. Get familiar with wild card masks.
  2. Memorize administrative distances of all routing protocols.
  3. Review the simple stuff, like 3way handshakes in tcp, setting up hrsp, ip helpers.
  4. Review Spanning Tree – Know what a root bridge is, know what VTP does, be sure you can explain the differences with RSTP.
  5. Review VLANs and be able to explain what a vlan is.

Employers know you can look things up in a pinch but what do you know off the top of your head that you can hit the ground running and fix a problem if it arises.

Tip: never answer “I can check it on Google”. This is a turn off for interviewers!

Trick: if you don’t know the answer, just say “I’ll look that up and I’ll get back to you with an answer” – you are not supposed to know everything but a good and proactive actitude always leaves a good impression.

Put yourself in their shoes, what will they need from you? Review the job description and target those things specific to the job your interviewing for.

 

The non technical part

The goal of an interview is to evaluate not only the technical knowledge of the candidate, but also the soft skills, the personality and the behavior. At the end you’ll be working on a team of people and be a good fit for the team is often more important than the technical skills.

Get ready for the non-technical questions and try to be honest and genuine, but also keep it professional. Check the company website to understand what they do and in which market they operate. Read few times the job description to understand what they need and how can you satisfy that need.

Some non technical questions that are often asked are along those lines:

  • Why did you choose a career as network engineer?
  • Why you think you can be an asset for our company?
  • What are your strengths and weaknesses?
  • Describe a difficult situation you had in your past jobs, how did you deal with it?
  • Have you ever had conflicts with your colleagues or manager? Why?
  • Describe a project or work that you’re particularly proud. Why was it a success?
  • Where do you see yourself in five years? (yes, this is the most hated one!)

Tip: prepare for those questions, it just take few minutes to think about the answers but will make a big difference when answering them with an assertive and confident tone.

 

Sample Interview Questions for Network Engineers

We get to the technical side now… here is our list of 20 Network Engineer Interview Questions:

  1. What is the subnet mask 10.2.1.3/22?
  2. What is the administrative distance of EIGRP, eBGP, iBGP?
  3. What is your favorite routing Protocol?
  4. In EIGRP, what is a Stuck in Active route?
  5. In OSPF, what is a totaly stubby area?  What does Area Zero do?
  6. Which internal routing protocol would use if you needed to route between Cisco and non-Cisco equipment?
  7. Explain what a 3-way handshake is in TCP?
  8. What is a VLAN trunking protocol?
  9. What is the different between 802.1q and ISL?
  10. Explain what is an Ether-Channel?
  11. What do you need to do to setup a VTP domain?
  12. What is Spanning Tree used for?
  13. What is a root bridge and why do you need one?
  14. What is needed on a router interface to allow DHCP to function on a subnet?
  15. Describe what a stateful firewall is?
  16. What is HSRP?  Is this an open standard?
  17. In a PIX/ASA, what are security levels used for?
  18. What two things are needed in a PIX/ASA firewall to allow traffic to pass from a higher security level to a lower security level?
  19. In IPSec VPNs, what is diffie hellman?  What is it used for?
  20. In an IPSec tunnel, what is main mode?

Check your knowledge taking our new quiz:

Do you know the answers to these questions? Have any more questions you would like to add? Leave a comment below and let us know the answers or more questions.

Network Engineer interviewFor more preparation questions check our new eBook Get That Network Engineer Job!

What you’ll learn:

  • The Interview Process explained
  • The Types of interviews and how they differ
  • Pre-Interview Work you have to do
  • Soft skills questions to prepare
  • Technical Questions (with answers)
  • What to do After the Interview
  • Preparation checklist: Interview DO’s and DON’Ts
submit button

 

Network Engineer Interview Questions
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About Joe

Senior Network Engineer, technology enthusiast, guitar and bass player. Joe Wilson is the creator of RouterFreak.com as well as other niche websites that can be found around on the Internets.

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90 comments

  1. How Bout this

    Which is safer and more secure?
    ipsec.
    vpnclient.
    anyconnect.

    which of the above will support 3g, 4g on an ASA while still retaining security?

  2. You initial comment of knowing ip addressing with a pen and paper no calculator.

    knowing basic, is essential to subnetting;
    by doing it with a pen and paper sends me several messages.

    1). it is OK to go out in the yard and use the sundail to tell the time (yes /no)?

    2). It is ok do devise subneting on the fly, while your running down the hallway?
    Android phones have an app for that
    (GET REAL)!
    If we devise a complex subnetting schem it is not done without great effort.

    3). it is ok to waste time.

    Why will we want to do Boolean Algebra, and binary conversions; you may need to use Binary conversion to HEX if. you intend to do route sumerization

  3. 9). isl is another,, ( it is just out of their) 802.1q is used on lessor older equipment, Trunking encyption currently most common is DOT1q.

  4. 2:) I suspected the older

    ebgp, ibgp may also be an irelevant topic, so I just glanced at my table of contence of my 2011 cisco press ccie r&s; igp may be the correct choice, as a current replacement to the older protocols

    Possibly a better usefull question may be: what is AD, and how does it get used, and in more depth explain MED.

  5. I was just asked question 1 in an interview. worded exactly the same with a different ip & mask.
    192.168.11.20/21, I put down 255.255.248.0 which is,

    (actualy an incorrect relpy):
    (since most interviewers are playing trivia).

    the question DID NOT ask the client to write the subnet mask with an alternet method to display a subnet mask.

    the questio simplt said “What is the subnetmask” /22 is a valid subnet mask correct? yes it is;

    the correct reply would be to simply point to the /22

  6. Second Section:

    11. What do you need to do to setup a VTP domain? To make switches exchange their VLAN information with each other, they need to be configured in the same VTP domain. Only switches belonging to the same domain share their VLAN information. When a change is made to the VLAN database, it is propagated to all switches via VTP advertisements. To maintain domain consistency, only one switch should be allowed to create (or delete, modify) new VLAN. This switch is like the “master” of the whole VTP domain and it is operated in Server mode. This is also the default mode. Other switches are only allowed to receive and forward updates from the “server” switch. They are operated in Client mode. In some cases, the network manager doesn’t want a switch to learn VTP information from other switches. He can set it to Transparent mode. In this mode, a switch maintains its own VLAN database and never learn VTP information from other switches (even the server). However, it still forwards VTP advertisements from the server to other switches (but doesn’t read that update). A transparent switch can add, delete and modify VLAN database locally.
    12. What is Spanning Tree used for? The Spanning Tree Protocol (STP) is a network protocol that ensures a loop-free topology for any bridged Ethernet local area network. The basic function of STP is to prevent bridge loops and the broadcast radiation that results from them. Spanning tree also allows a network design to include spare (redundant) links to provide automatic backup paths if an active link fails, without the danger of bridge loops, or the need for manual enabling/disabling of these backup links.
    13. What is a root bridge and why do you need one? Root Bridge is to act as the reference point in the network so that all switches can determine how far each of their ports are from the Root bridge and the port which has the lowest path cost is placed into a forwarding state all other ports that can lead to the Root bridge are blocked, ports in the switching topology that lead away from the Root Bridge may remain forwarding.
    14. What is needed on a router interface to allow DHCP to function on a subnet? DHCP functionality can be reliably configured on Cisco IOS devices. Cisco devices can be configured to act as DHCP servers, DHCP clients, or DHCP relay agents or even a combination of these. DHCP options like DNS servers, Domain name, lease time, etc. can be configured on Cisco devices. IP helper address activates the DHCP relay agent functionality on Cisco devices. DHCP relay agent options can be activated on Cisco devices so that supplementary services such as RBE functionality could be effective.
    15. Describe what a stateful firewall is? A stateful firewall (any firewall that performs stateful packet inspection (SPI) or stateful inspection) is a firewall that keeps track of the state of network connections (such as TCP streams, UDP communication) traveling across it. The firewall is programmed to distinguish legitimate packets for different types of connections. Only packets matching a known active connection will be allowed by the firewall; others will be rejected.
    16. What is HSRP? Is this an open standard? The Hot Standby Router Protocol, HSRP, provides a mechanism which is designed to support non-disruptive failover of IP traffic in certain circumstances. In particular, the protocol protects against the failure of the first hop router when the source host cannot learn the IP address of the first hop router dynamically. The protocol is designed for use over multi-access, multicast or broadcast capable LANs (e.g., Ethernet). HSRP is not intended as a replacement for existing dynamic router discovery mechanisms and those protocols should be used instead whenever possible. A large class of legacy host implementations that do not support dynamic discovery are capable of configuring a default router. HSRP provides failover services to those hosts. This is not open standard, its Cisco proprietary protocol.
    17. In a PIX/ASA, what are security levels used for?
    18. What two things are needed in a PIX/ASA firewall to allow traffic to pass from a higher security level to a lower security level?
    19. In IPSec VPNs, what is diffe helman? What is it used for?
    20. In an IPSec tunnel, what is main mode?

  7. Please find the answers which I have collected and up to my knowledge level. Please correct me if any answers are wrong. Also I'm weak in Security, so I haven't answered for the last 4 questions. If anyone know the answers for those questions, please post it. I have split the section into 2.

    Kindly clarify the answer for the DHCP question(Question No : 14). I have a confusion in that question. It would be appreciated if someone give the opt answer for that particular question.

    1. What is the subnet mask 10.2.1.3/22? The subnet mask of 10.2.1.3/22 is 255.255.252.0
    2. What is the administrative distance of EIGRP, eBGP, iBGP? The AD of EIGRP(Summary Route = 5), EIGRP(Internal = 90), EIGRP(External = 170), eBGP = 20 and iBGP = 200
    3. What is your favorite routing Protocol? OSPF
    4. In EIGRP, what is a Stuck in Active route? If the successor path is lost & there is no feasible successor path is available, router sends out query messages on all EIGRP enable interfaces & tries to find out an alternative path to the network. It is active state for that route.
    Now Router is waiting for reply from its neighbors. If reply is missing for 3 min, dat means router didn't get any reply from neighbors, then it becomes Stuck in Active.
    In this case, router reset the neighbor relationship with the router who didn't replied back the query messages sent by the router.
    To solve this problem, two method is used –
    a) Router summarization
    b) EIGRP Stub.
    To disbale the stuck in active timer, the following command is used –
    Router(config-router)# timers active-time disable.
    5. In OSPF, what is a totaly stubby area? What does Area Zero do? Totally Stubby area does not allow summary routes in addition to not having external routes, that is, inter-area (IA) routes are not summarized into totally stubby areas. The only way for traffic to get routed outside of the area is a default route which is the only Type-3 LSA advertised into the area. When there is only one route out of the area, fewer routing decisions have to be made by the route processor, which lowers system resource utilization. The backbone area (also known as area 0 or area 0.0.0.0) forms the core of an OSPF network. All other areas are connected to it, and inter-area routing happens via routers connected to the backbone area and to their own associated areas. It is the logical and physical structure for the 'OSPF domain' and is attached to all nonzero areas in the OSPF domain. The backbone area is responsible for distributing routing information between nonbackbone areas. The backbone must be contiguous, but it does not need to be physically contiguous; backbone connectivity can be established and maintained through the configuration of virtual links.
    6. Which internal routing protocol would use if you needed to route between Cisco and non-Cisco equipment? OSPF
    7. Explain what a 3-way handshake is in TCP? SYN,SYN-ACK,ACK
    8. What is a VLAN trunking protocol? VLAN Trunking Protocol (VTP) is a Cisco Layer 2 messaging protocol that manages the addition, deletion, and renaming of VLANs on a network-wide basis. Virtual Local Area Network (VLAN) Trunk Protocol (VTP) reduces administration in a switched network. When you configure a new VLAN on one VTP server, the VLAN is distributed through all switches in the domain. This reduces the need to configure the same VLAN everywhere. VTP is a Cisco-proprietary protocol that is available on most of the Cisco Catalyst Family products. The three VTP Modes are server, Client and Tranparent.
    9. What is the different between 802.1q and ISL? Trunks are used to carry traffic that belongs to multiple VLANs between devices over the same link. A device can determine which VLAN the traffic belongs to by its VLAN identifier. The VLAN identifier is a tag that is encapsulated with the data. ISL and 802.1Q are two types of encapsulation that are used to carry data from multiple VLANs over trunk links.
    10. Explain what is an Ether-Channel? Ether-Channel is a port link aggregation technology or port-channel architecture used primarily on Cisco switches. It allows grouping of several physical Ethernet links to create one logical Ethernet link for the purpose of providing fault-tolerance and high-speed links between switches, routers and servers. An EtherChannel can be created from between two and eight active Fast, Gigabit or 10-Gigabit Ethernet ports, with an additional one to eight inactive (failover) ports which become active as the other active ports fail. EtherChannel is primarily used in the backbone network, but can also be used to connect end user machines.

  8. can u send the answers for this

    What is the subnet mask 10.2.1.3/22?
    What is the administrative distance of EIGRP, eBGP, iBGP?
    What is your favorite routing Protocol?
    In EIGRP, what is a Stuck in Active route?
    In OSPF, what is a totaly stubby area? What does Area Zero do?
    Which internal routing protocol would use if you needed to route between Cisco and non-Cisco equipment?
    Explain what a 3-way handshake is in TCP?
    What is a VLAN trunking protocol?
    What is the different between 802.1q and ISL?
    Explain what is an Ether-Channel?
    What do you need to do to setup a VTP domain?
    What is Spanning Tree used for?
    What is a root bridge and why do you need one?
    What is needed on a router interface to allow DHCP to function on a subnet?
    Describe what a stateful firewall is?
    What is HSRP? Is this an open standard?
    In a PIX/ASA, what are security levels used for?
    What two things are needed in a PIX/ASA firewall to allow traffic to pass from a higher security level to a lower security level?
    In IPSec VPNs, what is diffe helman? What is it used for?
    In an IPSec tunnel, what is main mode?

  9. This is really very informative. The sample questions provided here are really good. Thanks.

  10. please send me more questions related to the network engineer interview for the 1 year experienced person

    thanks

  11. The company asked me five questions which were;

    You are tasked to setup a new site with the ip address of 192.168.10.0 for 100 users. What do you need to configure? How do you find the mac address of a device? What do you need to configure for a Cisco lightweight access point? Configure an IIS server for public use and allow internal use? Also asked me questions about which Cisco products I have used.

    • 1.What do you need to configure?
      I would use below command on router.
      ip dhcp excluded-address 192.168.10.0 192.168.10.20
      ip dhcp pool A
      network 192.168.10.0 255.255.255.0
      default-router 192.168.10.1
      dns-server 192.168.10.1 192.168.10.2 192.168.10.3
      lease 7 0 0 (days, hours, minutes) default is 7 days, I think.
      2.How do you find the mac address of a device?
      I would use sh ip arp on router or sh mac-address table.

      3,What do you need to configure for a Cisco lightweight access point?
      I would setup AAA and also define different vlan for different department, especially for guest vlan.

  12. A lot of times they may ask you questions about TCP and network performance, and whether you know about products like NetQoS SuperAgent. I watched a presentation by Kevin Davis of NetQoS on TCP, and it gave me everything I wanted to know about TCP and performance. I tried contact Kevin to get updates on what Microsoft is doing — but I think he retired or is in private consulting.

    So, know about TCP Syn/SynAck/Ack, windowing, slow start, fast retransmit, etc. for any company advertising TCP for a job.

    Bob Johnson

  13. What a brilliant article. I have an interview for a job soon and though I would research what questions might appear in my test. I know the answers to about 90% of the questions, feeling quite confident now. Not CCNA certified, but have studied CCNA and attended Cisco ASA and VOIP courses. Thanks for a pleasant read. J

  14. 1.What is the subnet mask 10.2.1.3/22?

    A: 255.255.252.0

    2.What is the administrative distance of EIGRP, eBGP, iBGP?

    Eigrp- 90, (5,170)

    Ospf-110

    Rip-120

    ebgp-20

    ibgp-200

    3.What is your favorite routing Protocol? Ospf- you can route any router

    4.In EIGRP, what is a Stuck in Active route?

    5.In OSPF, what is a totaly stubby area? What does Area Zero do? area only in its self

    6.Which internal routing protocol would use if you needed to route between Cisco and non-Cisco equipment? ospf

    7.Explain what a 3-way handshake is in TCP? sync sync ack sync – start off the information exchange

    8.What is a VLAN trunking protocol? propogates the def of vlan over the whole network

    9.What is the different between 802.1q and ISL? IDK?

    10.Explain what is an Ether-Channel? having multiple physical ports from a

    11.What do you need to do to setup a VTP domain? IDK?

    12.What is Spanning Tree used for? ensures a loop free topology on any lan

    13.What is a root bridge and why do you need one? IDK?

    14.What is needed on a router interface to allow DHCP to function on a subnet?

    15.Describe what a stateful firewall is?

    16.What is HSRP? Is this an open standard?

    17.In a PIX/ASA, what are security levels used for?

    18.What two things are needed in a PIX/ASA firewall to allow traffic to pass from a higher security level to a lower security level?

    19.In IPSec VPNs, what is diffe helman? What is it used for?

    20.In an IPSec tunnel, what is main mode?

    IDK 14-20 I know my wans just not my lans….. YET!

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