Networking interview questions

Networking 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 protocol?

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 , switched , 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 internetwork and intranetwork routing
protocols?
Which method does routing protocol use to determine shortest path?
What is distance vector routing protocol?
How do router 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 lie 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?

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?