Network engineer interview questions

OSPF

• Describe OSPF in your own words.
• OSPF areas, the purpose of having each of them
• Types of OSPF LSA, the purpose of each LSA type
• What exact LSA type you can see in different areas
• How OSPF establishes neighboor relation, what the stages are
• If OSPF router is stucked in each stage what the problem is and how to troubleshoot it
• OSPF hierarchy in the single or multi areas. Cool OSPF behavior in broadcast and nonbroadcast
• Draw the diagram of typical OSPF network and explain generally how it works, DR, BDR, election, ASBR, ABR, route redistribution and summarization

STP

• How it works and the purpose
• Diff types (SSTP, MSTP, RSTP) Cisco - PVST/PVST+
• root election
• Diff. port stages and timing for convergence
• Draw the typical diagram and explain how diff types of STP work
• What ports are blocking or forwarding
• How it works if there are topology changes

ACLs

• What are they
• Diff types
• Write an example if you want to allow and to deny…
• Well-known port numbers (DNS - 53 and etc…)

QOS

• What is that
• What is the diff b/w L2 and L3 QoS
• How it works

Network:

• Draw the typical network diagram you have to deal with
• explain how it works
• What part of it you are responsible
• firewall, what is that, how it works, how it is diff from ACLs
• What problems with the network you had had and how you solved it.
• What are the ways to troubleshoot the network, techniques, commands
• network security, ways to achieve it

Switching:

• VLANs
• STP
• How a L2 switch works with broadcast, unicast, multicast, known/unknown traffic
• VRRP, GLBP
• port monitoring and mirroring
• L3 switch, how it works
• PIM sparse and dense modes