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Network Engineer interview questions shared by candidates

## Top Interview Questions

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Junior Network Engineer was asked...3 October 2012

### How long do you plan to work here?

4 years

As long as possible

For ever

### All questions are mentions in the review and practice following coding questions for sure on leetcode.

7. Given a string, determine if it is a palindrome. - Complexity: Time: O(n) - Code #include #include int main(){ std::string strInput = "abcba"; int i=0, j=strInput.size()-1; while(i Less

3. convert the sentence to the modified pig-latin/goat-latin language. Complexity Time: O(n) + O(5) + O(k(k+1)/2) Considering total n characters in sentence. m characters/word O(n): Reading compelete sentence O(2): For vowel. Append ma O(3): For consonant. Append ma and 1st character 1+2+3+... k words = k(k+1)/2 Space: O(n) + 2O(m) + O(5) O(5): unordered_set of vowels 2O(m): Storing 2 word O(n): Storing complete sentence Code #include #include #include void AppendA(std::string&amp; strWord, int&amp; count){ int i = 0; strWord += "ma"; while(i++ us = {'a','e','i','o','u'}; //1st Letter is Vowel if (us.find(std::tolower(strParsed.at(0))) != us.end()) { strWord = strParsed; AppendA(strWord, ++count); } else //consonant { strWord = strParsed.substr(1,strParsed.size()); strWord += strParsed[0]; AppendA(strWord, ++count); } } int main(){ std::string strInput = "Adam wants to go to the university"; std::string strOutput, strWord, strParsed; int count = 0; for (auto&amp; i:strInput){ if (i == ' '){ Process(strParsed, strWord, count); strOutput += strWord + ' '; strWord = ""; strParsed = ""; } else //Store word in strParsed { strParsed += i; } } Process(strParsed, strWord, count); strOutput += strWord ; std::cout&lt;&lt;"Converted string="&lt; Less

1. You receive a vector/ array and 2 numbers, eg 2 and 5. Between those 2 positions in the vector (2 and 5) you have to reverse the order of the elements. Code #include #include #include using vec = std::vector; using itr = std::vector::iterator; int main(){ vec v = {1,2,9,8,4,5,23,5,252,445,677,5}; //Find position of 2 itr it1 = std::find(v.begin(), v.end(), 2); //O(n) //Find position of 5 itr it2 = std::find(v.begin(), v.end(), 5); //O(n) std::reverse(it1+1, it2); //O(n) for (auto i:v) std::cout&lt; Less

### a detailed troubleshooting scenario for VPN was asked. a site-to-site VPN, user from one site cannot get to a resource on another site.

Hello, Can anyone tell me the best link to study troubleshooting scenarios from?

#sh vlan brief

There was no one answer for this, and since I didn't know much about vpns, the interviewer guided me through the possible answers! Less

### How does STP work...how does it know who will control everything?

It disables redundant paths and only leaves one broadcast path in a mesh network. It then enables a previous blocked path if one of the primary links becomes disconnected. This creates a network that won't cause broadcast storms but still provide redundancy. Less

STP operates at the Data Link layer of the OSI model which prevents traffic loops. STP chooses only one root switch/bridge, out of which all data paths span out logically getting the data to the target the quickest and detect and correct link failures when a switch/bridge fails...STP stands for Spanning Tree Protocol. The root is chosen based on its BID( Bridge ID) which is the combination of a 2 byte priority field and the bridge/switch MAC address....Since all switch/bridges on the network start out with the same priority, the one with the lowest MAC address becomes the root bridge. Less

STP is basically used for loop prevention and to prodive redundancy. Devices participating in STP perform a root bridge election process. Device having the lowest priority will be choosen as the root bridge. If every device participating in STP have the same priority value, device with the lowest mac-address becomes the root bridge. The root bridge will be responsible to make th overall traffic flow decision on the LAN. Non-root bridges use a lowest cost path to reach the root bridge. This cost is dependent on the interface speed. Topological changes downstream from the root bridge is communicated to the root bridge. Less

Port 21

both 20 and 21

20 and 21

### bgp, mpls,vpn

what do you think ? If i was there 4 hours.

I mean what were the topics they focused and can you please elaborate.

Tons of questions about ibgp behavior , ebgp ,mpls ldp , te , mpbgp , sec vpn and other protocols. Less

### Coding questions are from Med-Hard LC Networking - BGP/OSPF/Redundancy, STP, IPv6

The key in these questions is to cover the fundamentals, and be ready for the back-and-forth with the interviewer. Might be worth doing a mock interview with one of the Facebook or ex-Facebook Network Engineer experts on Prepfully? They give real-world practice and guidance, which is pretty helpful. prepfully.com/practice-interviews Less

Can you share some details around system design ? Was it realted to bringing up a new data center or discussion about your previous projects ? Less

Practice 50-100 LC Easy to Med questions. Should put you on the track to success. Networking - Read CCNP guides for OSPF and BGP. Expect questions in depth and very specific. Less

### · BGP/TCP/IP protocols/route reflectors · Network hardware and software – switches, chips, etc. · Network infrastructure · Troubleshooting · Linux / automation, Scripting(Regex will be helpful)

I did well.

Basic String manipulatiob

Could you please tell me what kind of questions faced in a coding interview ? Please let me know as earliest as possible. Less

### Q: Vlans-- The interviewer asked me the following Scenario. a. Two Switches are connected. b. There are Two Vlans. Vlan 10 & Vlan 20. c. Vlan 10 IP: 192.168.1.0 /24 | Vlan 20: 192.168.2.0 /24 d. Users in Vlan 10 can communicate with users in Vlan20.

My Response: I asked him a return query stating that is there any L3 Device as he mentioned the IP address. He answered No. I was confident that the Users in Vlan 10 will not able to communicate with Users in Vlan20 until and unless if there is a L3 device such as Router or a L3 Switch or multi layer Switch. I explained him the same but still he said that its communicating. He also informed that there are only Two Switches which are L2 Switches. 2. Another Question: What is you Favourite Routing Protocol? Answered: EIGRP. 3. What is FC condition? Ans: FD &gt; AD (Feasible Condition &gt; Advertising Distance). Instead of Saying Advertising Distance, I said Administrative Distance (which is 90 for EIGRP). 4. What are the Requirements for an EIGRP Router to form the Neighbors? Ans: Hello Packets | AS number should be same | K values must match. Mentioned Hold timers which is not a required. Cheers, Raja. Less

Yes this is possible through inter-vlan routing. 1st need to take 2 MLS switch, connect them, create vlans and configure IP addresses for both vlan. Less

Yes this is possible through inter-vlan routing. 1st need to take 2 MLS switch, connect them, create vlans and configure IP addresses for both vlan. Less