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Network engineer Interview Questions

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Phone Interview: 1. What is a beacon frame? It is a management frame sent out by an AP that is used to keep the devices on a wireless network associated with it, in sync. This is essential for CSMA/CA 2. What is the difference between 2.4 GHz and 5 Ghz frequencies on a wireless network? Higher Frequencies have more attenuation through Free space. 2.4 GHz can travel further. 5 GHz is a less crowded frequency band. Therefore less prone to interference 3. What are the non-overlapping channels in the 2.4 GHz frequency band? Channels 1, 6 and 11 4. How do packets travel across a network? ( Explain using an ICMP example, use all the protocols. that are involved. DHCP, ARP etc. Keep in mind the OSI model) 5. What is the difference between STP and RSTP? Technical Interview: 1. If you were to take an RF Wireless survey, would you do it when there were people in the room or when the room was empty? Always when people are in the room, humans are 60-70% water and that means more attenuation. This will be an efficient survey, only if people are in the room. 2. What happens when you type www.google.com into your computer? 3. What does the 's' in https signify? SSL communication between host and server 4.(Scenario Based) A host is trying to connect to a computer across a VPN tunnel but unfortunately it cannot access the resource. What could be the problem,assuming that the VPN tunnel is setup correctly? The correct answer is the hosts file on the computer has an incorrect mapping of the name to ip. You will know this when you ping the name of host and it resolves to a different ip. 5. (Scenario Based) A firewall in a corporate environment was one day replaced with a Meraki firewall. Now clients are no longer able to access the web server, The configuration on the different firewalls are identical. What could be the problem? The ARP cache on the modem still points to an old mapping of the Firewall. The MAC address had now changed, Therefore in order to rectify the problem, power off and power on the modem. 6. What is gratuitous ARP? 7. What are the different modes with IPSec? What is IKE Phase 1 and IKE Phase 2? main mode and quick mode 8. (Scenario-Based ), three switches are connected together in a triangle design, A, B and C, Who becomes the Root bridge? What is the default priority on Cisco switches? Can a switch have a priority of 0? When the speed of the links are changed, does the root port also change? 9. What is the difference between PVST and PVST+? 10. Name one channel in a 5 GHz band? 11. Explain to me how DNS works? Cultural interview: 1. (Scenario-based) There is a set of core and distribution switches, there are three VLANs spanned across all switches, RSTP is functioning correctly, a user connected to VLAN 2 cannot access the internet, what could be the problem? Ans: you must deduce that if everything is configured correctly and there are no physical issues with the network, the correct answer is that there is a rogue DHCP server in VLAN 2. You need to shutdown the port connected to the rogue DHCP server. First, find out the MAC address of the rogue DHCP server from the arp cache of the host computer. arp -a. Secondly, from the CAM address table of the switch, see which port is associated with the MAC address. Thirdly, block the port.Fourthly, ipconfig /release and ipconfig /renew on the host computer to get a legitimate IP address from the real DHCP server in VLAN 2. Alternative solution would be to enable DHCP Snooping. 2. if the logs on a linux apache server are suddenly not being written to ? what could be the problem? a. permissions issue b. disk space requirements c. is apache service running? d. has the location of the log file been changed on the apache configuration file? e. Check the logrotate feature.

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Hi, Thank you for sharing! Can you tell me the best link to study troubleshooting scenarios from?

How do you influence the routing on the carrier side when your routers talk with two different ISPs?

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No technical questions were asked. Was drilled extensively by a panel about previous work scenarios and working experience.

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Behavioural question, like explain your self and your history some background on Telco experience Technical background check and ask for some certifications Technical questions on MPLS, BGP and OSPF Some layer 2 questions VLAN, Spanning Tree Some ISP related routing questions (route influence) Some team building activities related questions Leadership examples in your past roles and issues

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work experience, previous work history.

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Technical questions on Cisco ISE and DMVPN and BGP

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What is a firewall?

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How TCP 3 way handshake happened?

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Why is a router stuck at 2-way state when it runs OSPF?

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how do OSPF prevent loops? what's the types of OSPF areas and LSAs belong to them? Given a topology (the guy described a simple but tricky topology) with area, describe types of LSA can exist in the topology and how OSPF do loop prevention in the situation.

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