Networking Interview Questions

Basics
· Can you define protocol?
· Can you explain the concept of OSI layer?
· Can you explain the different layers in OSI model?
· Can you explain Application layer in OSI model?
· Can you explain Presentation layer in OSI model?
· Is it compulsory that compression, encryption and translation functions will be
used during communication?
· Can you explain Session layer in OSI model?
· What’s the concept of Simplex, Half Duplex and Full Duplex dialogs?
· What are the different types of dialogs in Session layer?
· Can you explain Transport layer in OSI model?
· Can you explain the concept of Congestion?
· Can you explain Network Layer?
· Can you explain Data link Layer?
· Can you explain the Physical layer?
· Can you explain what an IP address is?
· How to convert Decimal to Binary?
· How many IP addresses can come in IPV4?
· Can you explain the concept of Unicast IP address?
· Can you explain the concept of IP multicasting or multicast IP address?
· How many different types of subnet classful networks are present?
· What are the IP address ranges for public and private IP address?
· Why do we need class and how many different types of class exists?
· How are the IP addresses distributed between different classes?
· Can you explain what is classful IP addressing?
· Can you explain the concept of subnetting?
· What are the advantages of using subneting?
· If the host has the subnet ID why do we need a subnet mask?
· How is network address calculated from the subnet?
· What is the advantage of using classless addressing over classful addressing
scheme?
· Can you explain the concept of CIDR?
· Twist: - Can you explain superneting?
· Can you explain concept of custom subneting?
· What is the implication of increasing and decreasing subnet Bits?
· Why do we need to subtract two from number of hosts?
· Can you explain the concept of VLSM?
· Can you explain IP packet in detail?

Routers
· Can you explain the concept of DPU, Segments, Datagram, Frame and packet?
· What is IP datagram fragmentation and MTU?
· Can you explain in detail with example how data fragmentation works?
· Larger the IP datagram less the overhead, is it true or false?
· What is the minimum size of MTU bytes?
· Can you explain how optimal MTU size is calculated?
· How does the IP message finally reassemble?
· Can you explain the concept of Repeaters, Hubs, Bridges, Switches and Routers?
· On what layers do router, switches, bridges and hubs operate?
· Can you explain the concept of Layer 3 switches?
· What are CSU, DSU and TSU?
· What are the basic components of the router?
· Can you explain the WAN and LAN Interface in Routers?
· What are DB-15, DB-60 and RJ-45 in CISCO routers?
· Can you explain the concept of TTL?
· What is the concept of ICMP packets?
· Which operating system does CISCO have?
· Can you explain the concept of NAT?
· How is NAT implemented?
· Can you explain how actually NAT works?
· Why does collision occur in HUBS and repeaters?
· Can you explain the concept of Collision domain?
· What is the concept of routing tables?
· What is the use of route print?
· Can you explain how in detail how routing table looks like?
· How can you see route tables on the router?
· Can you explain the concept of static and dynamic routing?
· When to use Static routes and dynamic routes?
· How do you configure static routes on a router?
· Can you explain static default routes?
· What is the advantage of using Static default routes?
· Why do workstations have route tables?
· What is the concept of gateway of last resort?
· Can you explain the concept of routing protocol?
· What activities does routing protocol perform?
· What metrics are used by routing protocols to determine the best path?
· Can you explain what is interior and exterior routing protocols?
· Can you explain the concept of intradomain and interdomain routing protocols?
· Can you explain the concept of internet work and intranet work routing protocols?
· Which method does routing protocol use to determine shortest path?
· What is distance vector routing protocol?
· How do routers share information in Distance Vector routing?
· What is the main issue with routing by rumor?
· Can you explain the count-to- infinity problem in distance vector?
· How is metric or the cost calculated for Distance Vector routing protocol?
· What is the main issue with hop count metric issue?
· Can you explain how Link-State routing protocols work?
· Can you explain the concept of broad cast and multi-cast?
· Can you tell which protocols falls in Distance vector and which in Link-State?
· What’s the difference between distance vector and link-state protocol?
· Can you explain difference between Single path and Multipath?
· Can you explain route summarization?
· How are the series of IP combined in to one route path in route summarization?
· Can you explain RIP protocol?
· How is route table populated by RIP protocol?
· Can you explain convergence in networks?
· Can you explain RIP timers in detail?
· Can you explain routing loop issue in RIP protocol?
· How do we avoid routing loop issue in RIP?
· In RIP why do we have HOP count of 15?
· How do we disable auto-summarization in RIP?
· Can you explain IGRP?
· How does IGRP work?
· How many timers does IGRP have?
· How does IGRP calculate metric?
· Can multiple instance of IGRP run on one physical router?
· How is load balancing done in IGRP?
· What’s the command to configure IGRP?
· Can you explain EIGRP?
· What does neighbor terminology mean in EIGRP?
· What are different types of packets in EIGRP?
· How does EIGRP protocol update route information to its neighbors?
· What is the concept of successor in EIGRP?
· What is DUAL in EIGRP?
· Can you explain reported distance (RD), feasibility distance (FD) and Feasibility
condition (FC)?
· Can you explain the concept of successor and feasible successor?
· Can you explain passive and active route states?
· What is SIA or stuck in active?
· How do packets and timers in EIGRP work?
· What are the different tables used in EIGRP?
· Can you explain EIGRP metrics?
· Can you explain how EIGRP finds its successor and feasible successor?
· Can you explain Active and Passive route?
· Can you explain OSPF?
· How does OSPF populate route table?
· What are the different tables in OSPF?
· Can you explain different areas in OSPF?
· Can you explain different router types in OSPF?
· Can you explain Designated Router and Backup designated router?
· Can you explain different router states in OSPF?
· Can you explain different OSPF packet types?
· What are the different types of OSPF timers?
· How SPF algorithm does the route determination?
· Can you explain autonomous system?
· What are different types of dynamic protocols?
· Can you explain autonomous numbers in EGP?
· What is BGP?
· What is the concept of BGP speakers and Peers?
· What is EBGP and IBGP?
· What is RIB?
· Can you explain the concept of BGP confederations?
· What are BGP path attributes?
· What is the concept of NLRI?
· How are routing neighbors discovered in BGP?
· Can you explain how BGP does the decision process?
· What is the concept of redistribution?
· Can you explain the concept of one way redistribution and mutual distribution?
· How does metric translation takes place in redistributing routes?

Firewall
· Can you define what a FIREWALL is?
· What are the different types of firewalls?
· Can you explain packet filtering firewall?
· Can you explain circuit level gateway?
· Can you explain stateful inspection?
· What is Application Gateway?
· Is NAT a firewall?
· Are personal firewall actually firewalls?
· Can you explain the concept of demilitarized zone?
· What is the meaning of bastion host?
· What are the different types of firewall architectures?
· Can you explain dual home architecture?
· Can you explain screened host architecture?
· Can you explain screened subnet architecture?
· What is the use of perimeter area?
· What is IP spoofing and how can it be prevented?
· Which firewall have you worked with?

VPN
· Can you explain the difference between trusted and untrusted networks?
· Can you define in short what VPN is?
· What are the different types of VPN?
· What requirements should a VPN fulfill?
· How many ways are there to implement VPN architecture?
· What are the different ways authentication mechanism in VPN?
· Can you explain the basic of encryption in VPN?
· What’s the difference between Symmetric and Asymmetric cryptosystem?
· What are the different symmetric algorithms?
· What are the disadvantages of symmetric algorithms?
· What are the different asymmetric algorithms?
· Can you explain different components in PKI?
· What is a digital certificate?
· Can you explain tunneling?
· What is the concept of HA and FA in VPN tunneling?
· Can you explain VPN tunneled packet in detail?
· Can you explain voluntary and compulsory tunnels?
· Can you explain static and dynamic tunnels?
· Can you explain encapsulating, carrier and passenger protocol?
· On which layer does L2F, PPTP and L2TP operate?
· Can you explain PPP protocol?
· Can you explain PPP link process step by step?
· Can you explain PPP packet format?
· How does PPP use LCP for link control?
· Can you explain PPTP (Point-to-Point Tunneling Protocol)?
· What is GRE in PPTP?
· How does PPTP encapsulate data?
· Can you explain CHAP?
· Can you explain PAP?
· What does PPTP use for encryption and authentication?
· What is a L2F protocol?
· Can you explain the broader steps of how L2F establishes the tunnel?
· Can you explain how L2F data tunneling process works?
· How do we do encryption and authentication in L2F?
· Can you explain L2TP?
· Can you define LAC and LNS?
· How does L2TP process?
· How do we do encryption and authentication in L2TP?
· Can you explain what IPSec is?
· Can you give an overview of various components in IPSec?
· In IPSec what is SAD, SPD and SA’s?
· Can you explain in a generic manner the packet of IPSec?
· Can you describe the Authentication Header (AH) Protocol?
· What is ESP (Encapsulating Security Payload)?
· What is Transport and Tunnel mode?
· Can you explain IKE (Internet Key Exchange)?
· Can you explain IKE phases?
· Can you explain IKE modes?
· Can you explain transport and tunnel mode in detail with datagram packets?

Protocols and other questions
· What is NetBIOS protocol?
· Can you explain what the use of IGMP Protocol is?
· What are the different types of host in multicasting?
· Can you explain Ping and Tracert?
· How do you continuously ping an IP Address?
· How does Tracert actually work?
· What is the use of RTP and RTCP Protocol?
· Can you explain RTP in Detail?
· Can you explain RTP multiplexing in detail?
· Can you explain format of RTP and RTCP packets?
· Can you explain RSVP?
· Can you explain in detail how RSVP actually works?
· Can you explain RPC (Remote Procedure Calls)?
· Can you explain the RPC and Client server Architecture?
· Can you explain TCP IP Protocol?
· Can you explain the architecture of TCP IP Protocol?
· Can you explain TCP header in detail?
· Can you explain IP protocol?
· Can you explain the concept of CDMA?
· Can you explain the concept of DHCP?
· How does DHCP work?
· How can we configure DHCP?
· What is DNS?
· How do we control USB through a network?
· What is the difference between Windows 2000 and Windows 2003?
· What is a difference between a domain and workgroup?