Networking and Unix interview questions

What is UTP?

UTP — Unshielded twisted pair 10BASE-T is the preferred Ethernet medium of the 90s. It is based on a star topology and provides a number of advantages over coaxial media:

It uses inexpensive, readily available copper phone wire. UTP wire is much easier to install and debug than coax. UTP uses RG-45 connectors, which are cheap and reliable.

What is a router? What is a gateway?

Routers are machines that direct a packet through the maze of networks that stand between its source and destination. Normally a router is used for internal networks while a gateway acts a door for the packet to reach the ‘outside’ of the internal network

What is Semaphore? What is deadlock?

Semaphore is a synchronization tool to solve critical-section problem, can be used to control access to the critical section for a process or thread. The main disadvantage (same of mutual-exclusion) is require busy waiting. It will create problems in a multiprogramming system, where a single CPU is shared among many processes.

Busy waiting wastes CPU cycles.

Deadlock is a situation when two or more processes are waiting indefinitely for an event that can be caused by only one of the waiting processes. The implementation of a semaphore with a waiting queue may result in this situation.

What is Virtual Memory?

Virtual memory is a technique that allows the execution of processes that may not be completely in memory. A separation of user logical memory from physical memory allows an extremely large virtual memory to be provided for programmers when only a smaller physical memory is available. It is commonly implemented by demand paging. A demand paging system is similar to a paging system with swapping. Processes reside on secondary memory (which is usually a disk). When we want to execute a process, we swap it into memory.

Explain the layered aspect of a UNIX system. What are the layers? What does it mean to say they are layers?

A UNIX system has essentially three main layers:

� The hardware

� The operating system kernel

� The user-level programs

The kernel hides the system’s hardware underneath an abstract, high-level programming interface. It is responsible for implementing many of the facilities that users and user-level programs take for granted.

The kernel assembles all of the following UNIX concepts from lower-level hardware features:

� Processes (time-sharing, protected address space)

� Signals and semaphores

� Virtual Memory (swapping, paging, and mapping)

� The filesystem (files, directories, namespace)

� Pipes and network connections (inter-process communication)

Network programming interview questions

Question 1: How does the race condition occur?

It occurs when two or more processes are reading or writing some shared data and the final result depends on who runs precisely when.

Question 2: What is multiprogramming?

Multiprogramming is a rapid switching of the CPU back and forth between processes.

Question 3: Name the seven layers of the OSI Model and describe them briefly.

Physical Layer - covers the physical interface between devices and the rules by which bits are passed from one to another.

Data Link Layer - attempts o make the physical link reliable and provides the means to activate, maintain, and deactivate the link.

Network Layer - provides for the transfer of information between end systems across

some sort communications network.

Transport Layer - provides a mechanism for the exchange of data between end system.

Session Layer - provides the mechanism for controlling the dialogue between applications

in end systems.

Presentation Layer - defines the format of the data to be exchanged between applications

and offers application programs a set of data transformation services.

Application Layer - provides a means for application programs to access the OSI environment.

Question 4: What is the difference between TCP and UDP?

TCP and UDP are both transport-level protocols. TCP is designed to provide reliable

communication across a variety of reliable and unreliable networks and internets.

UDP provides a connectionless service for application-level procedures. Thus, UDP is basically

an unreliable service; delivery and duplicate protection are not guareented.

Question 5: What does a socket consists of?

The combination of an IP address and a port number is called a socket.

Networking interview questions

Q1. Name of seven layers in Open System Interconnection model.

A. They are Application, Presentation, Session, Transport, Network, Data link, and Physical.

Q2. What is the time complexity of matrix multiplication ?

void Mult_Matrix(matrix A, matrix B, matrix C)
{
int i, j, k;
for ( i = 1; i < N; i++)
for ( j = 1; j < N; j++ )
{
C[i][j] = 0;
for ( k = 0; k < N; k++ )
C[i][j] = A[i][j]*B[k][j];
}
retrun;
}

A. The time comlexity of matrix mulitiplication is O(N^3)

Q3. What is the null pointer in C++ ?

A. The null pointer is a special C++ pointer value that can be used for any pointer that doesn’t pointer anywhere. It can be written as the constant NULL form stlib.h

Q4. What is the goal of the shortest distance algorithm ?

A. The goal is to completely fill the distance array so that for each vertex v, the value of distance[v] is the weight of the shortest path from start to v.

Q5. What is the difference between an abstract class and an interface?

A.

An abstract class may have fields and some implemented methods.

An interface has no implementation; only constants and method declarations.

Networking and protocols interview questions

Q: What are the seven layers of the OSI model?

A: The layers are physical, data link, network, transport, session, presentation, and application layers.

Q: In the TCP client-servel model, how does the three-way handshake work in opening connection?

A: The client first sends a packet with sequence "x" to the server. When the server receives this packet, the server will send back another packet with sequence "y", acknowledging the request of the client. When the client receives the acknowledgement from the server, the client will then send an acknowledge back to the server for acknowledging that sequence "y" has been received.

Q: What is the purpose of exchanging beginning sequence numbers during the the connection in the TCP client-server model?

A: To ensure that any data lost during data transfer can be retransmitted.

Q: How does Asynchronous Transfer Mode (ATM) work?

A: ATM works by transmitting all traffic in small, fixed-sized cells. These small, fixed-size cells reduces queuing delay and can be switched quickly. ATM fits into layer 2 of the OSI model and provides functions for framing and error correction. At the port interface, ATM switches convert cells into frames, and vice versa. ATM provides Quality of Service and traffic shaping.

Q: Given a Class B Network with subnet mask of 255.255.248.0 and a packet addressed to 130.40.32.16, what is the subnet address?

A: Take the 2 addresses, write them in binary form, then AND them. The answer is 130.40.32.0

Wireless engineer interview questions

1. Describe your home WLAN setup.(Pay attention to candidate’s confidence. Plus if the candidate built it himself. Plus if the network is secured additionally, regardless of the protocols used. Plus if the candidate fought poor coverage.)
2. Ad-hoc vs. infrastructure topology. Advantages and disadvantages. Ad-hoc networks are easy to set up. By definition ad-hoc WLANs do not require access point, so they are cheaper. With infrastructured WLANs one can connect to wired LAN, enable wireless roaming for office workers, centralize WLAN management, boost the range.
3. Your preferred brand for wireless cards and access points. (An experienced candidate will be able to come up with strong argument to defend his preferences. He will point to the past projects as well.)
4. Range and throughput of 802.11a, 802.11b and 802.11g networks. The official spec for 802.11a is 54 Mbps and 25-75 feet indoors. The official spec for 802.11b is 11 Mbps and 100-150 feet indoors. The official spec for 802.11g is 54 Mbps and 100-150 feet indoors. An experienced candidate will provide his own observations.
5. How do you secure a wireless network? Forbid SSID broadcasting, enable MAC-level access where appropriate, enable WEP, enable 802.11i where available, enable firewalls, enable WPA.
6. What does Wi-Fi stand for? Wireless Fidelity.
7. What is 802.11i? It’s a new IEEE standard defining wireless network security.
8. What are the recommended channels if you’re setting up three WLANs and want minimum interference? 1, 6 and 11 for the US, 1, 7 and 13 for Europe and 1, 7 and 14 for Japan.
9. What are your preferred tools for wardriving? Somewhere the names Kismet, *stumbler or others should come up. Ask the

Network engineer/architect interview questions

1. Explain how traceroute, ping, and tcpdump work and what they are used for?
2. Describe a case where you have used these tools to troubleshoot.
3. What is the last major networking problem you troubleshot and solved on your own in the last year?
4. What LAN analyzer tools are you familiar with and describe how you use them to troubleshoot and on what media and network types.
5. Explain the contents of a routing table (default route, next hop, etc.)
6. What routing protocols have you configured?
7. Describe the commands to set up a route.
8. What routing problems have you troubleshot?
9. How do you display a routing table on a Cisco? On a host?
10. How do you use a routing table and for what?
11. What is a route flap?
12. What is a metric?
13. When do you use BGP, IGRP, OSPF, Static Routes?
14. What do you see as current networking security issues (e.g. NFS mounting, spoofing, one time passwords, etc.)?
15. Describe a routing filter and what it does.
16. Describe an access list and what it does.
17. What is a network management system?
18. Describe how SNMP works.
19. Describe the working environment you are currently in, e.g. frequent interruptions, frequent priority shifting, team or individual.
20. What do you use to write documentation? Editor? Mail reader?
21. What platform (s) do you currently work on at your desk?
22. How do you manage multiple concurrent high level projects?
23. Describe a recent short term stressful situation and how you managed it.
24. How do you manage a long term demanding stressful work environment?
25. Have you worked in an assignment based environment, e.g. work request/trouble ticket system, and if so, describe that environment.
26. Describe what network statistics or measurement tools you are familiar with and how you have used them.
27. Describe what a VPN is and how it works.
28. Describe how VoIP works.
29. Describe methods of QoS.
30. How does ToS bit work?

Interview questions for network engineer

1. Describe the OSI model.
2. What is the difference between a repeater, bridge, router? Relate this to the OSI model.
3. Describe an Ethernet switch and where it fits into the OSI model.
4. What is a VLAN? What is an ELAN? What is the difference?
5. Relate FDDI/ATM/SONET to the OSI model.
6. Explain how to configure a host network interface (e.g. IP address, netmask, broadcast address)?
7. Describe Ethernet packet contents: min/max size, header.
8. Describe TCP/IP and its protocols.
9. Describe ATM and what are its current advantages and disadvantages.
10. Describe SONET.
11. What are the maximum distances for CAT5 cabling?
12. Describe UDP and TCP and the differences between the two.
13. What is your current IP address? Hoiw do you find that out on different OSs?
14. Describe what a broadcast storm is.
15. Describe what a runt, a giant, and a late collision are and what causes each of them.
16. How do you distinguish a DNS problem from a network problem?
17. Describe the Bandwidth Delay problem.
18. Describe the principle of multi-layer switching.
19. Describe the purpose and basic functionality of things like HSRP, VRRP etc.

Solaris interview questions

1. List the files in current directory sorted by size ? - ls -l | grep ^- | sort -nr
2. List the hidden files in current directory ? - ls -a1 | grep "^\."
3. Delete blank lines in a file ? - cat sample.txt | grep -v ‘^$’ > new_sample.txt
4. Search for a sample string in particular files ? - grep “Debug” *.confHere grep uses the string “Debug” to search in all files with extension“.conf” under current directory.
5. Display the last newly appending lines of a file during appendingdata to the same file by some processes ? - tail –f Debug.logHere tail shows the newly appended data into Debug.log by some processes/user.
6. Display the Disk Usage of file sizes under each directory in currentDirectory ? - du -k * | sort –nr (or) du –k . | sort -nr
7. Change to a directory, which is having very long name ? - cd CDMA_3X_GEN*Here original directory name is – “CDMA_3X_GENERATION_DATA”.
8. Display the all files recursively with path under current directory ? - find . -depth -print
9. Set the Display automatically for the current new user ? - export DISPLAY=`eval ‘who am i | cut -d"(" -f2 | cut -d")" -f1′`Here in above command, see single quote, double quote, grave ascent is used. Observe carefully.
10. Display the processes, which are running under yourusername ? - ps –aef | grep MaheshvjHere, Maheshvj is the username.
11. List some Hot Keys for bash shell ? - Ctrl+l – Clears the Screen. Ctrl+r – Does a search in previously given commands in shell. Ctrl+u - Clears the typing before the hotkey. Ctrl+a – Places cursor at the beginning of the command at shell. Ctrl+e – Places cursor at the end of the command at shell. Ctrl+d – Kills the shell. Ctrl+z – Places the currently running process into background.
12. Display the files in the directory by file size ? - ls –ltr | sort –nr –k 5
13. How to save man pages to a file ? - man | col –b > Example : man top | col –b > top_help.txt
14. How to know the date & time for – when script is executed ? - Add the following script line in shell script.eval echo "Script is executed at `date`" >> timeinfo.infHere, “timeinfo.inf” contains date & time details ie., when script is executed and history related to execution.
15. How do you find out drive statistics ? - iostat -E
16. Display disk usage in Kilobytes ? - du -k
17. Display top ten largest files/directories ? - du -sk * | sort -nr | head
18. How much space is used for users in kilobytes ? - quot -af
19. How to create null file ? - cat /dev/null > filename1
20. Access common commands quicker ? - ps -ef | grep -i $@
21. Display the page size of memory ? - pagesize -a
22. Display Ethernet Address arp table ? - arp -a
23. Display the no.of active established connections to localhost ? - netstat -a | grep EST
24. Display the state of interfaces used for TCP/IP traffice ? - netstat -i
25. Display the parent/child tree of a process ? - ptree Example: ptree 1267
26. Show the working directory of a process ? - pwdx Example: pwdx 1267
27. Display the processes current open files ? - pfiles Example: pfiles 1267
28. Display the inter-process communication facility status ? - ipcs
29. Display the top most process utilizing most CPU ? - top –b 1
30. Alternative for top command ? - prstat -a

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

Solaris interview questions

1. What does the pkgadd command do?
2. How do you create a solaris package?
3. How do you view shared memory statistics?
4. How do you get system diagnostics information?
5. What is OBP and how do you access it?
6. What is LOM and how do you access it?
7. What is VTS?
8. What is an alternative to the “top” command on Solaris?
9. What is /etc/system for?
10. What does ndd do?
11. What does init 5 do?
12. What does init 0 do?
13. How do you boot from CD-ROM?
14. What is jumpstart?
15. How do you boot from a Network with jumpstart?
16. What is JASS?
17. What is the difference between NFS version 2 and NFS version 3?
18. What is RPC? Why do I need it?
19. Are kernel parameters tunable during runtime?
20. What does fmthard do?

Network administrator interview questions

1. What is the difference between layer 2 and layer 3 in the OSI model?
2. What is the difference between a hub, switch, and router?
3. What is a VLAN?
4. What is the difference between TCP and UDP?
5. How do you distinguish a DNS problem from a network problem?
6. What is a runt, Giant, and collision?
7. What is a broadcast storm?
8. What is the purpose of VRRP?
9. What is a VPN?
10. What information about a peer would I need to establish a VPN?
11. What is a full-class C in CIDR notation?
12. What is a default route?
13. What is a metric?
14. What is a MAC address?
15. What is ARP/RARP?
16. Describe a TCP connection sequence
17. What is MTU?
18. What other TCP setting can you modify besides MTU to shorten packets?

Cisco-specific network engineer questions

1. What is a wildcard mask, and how is it different from a netmask?
2. How do you configure a Cisco switch or router? What are the steps needed?
3. How would I place an interface into trunking mode?
4. How do you shutdown an interface on a router or switch?
5. What is VTP?
6. What is VMPS?
7. What is SPAN/RSPAN?
8. What is flow/netflow?
9. What is TACACS? Radius?

Security interview questions for network admin

1. What is a firewall?
2. Describe, genrally, how to manage a firewall
3. What is a Denial of Service attack?
4. What is a “spoofed” packet?
5. What is a SYN Flood?
6. What do you do if you are a victim of a DoS?
7. What is GPG/PGP?
8. What is SSH?
9. What is SSL? How do you create certificates?
10. What would you do if you discovered a UNIX or Network device on your network has been compromised?
11. What would you do if you discovered a Windows system on your network has been comrpromised?
12. What is DNS Hijacking?
13. What is a log host?
14. What is IDS or IDP, and can you give me an example of one?
15. Why are proxy servers useful?
16. What is web-caching?

Network developer interview questions

1. What ports does FTP traffic travel over?
2. What ports does mail traffic utilize?
3. What ports do HTTP and HTTPS use?
4. Why is NTP required in an NFS network?
5. Name some common mal software on the server side
6. What is CPAN? How do you access it?
7. What is PEAR?
8. What advantages does mod_perl have over a perl CGI?
9. What is required to do SSL in Apache 1.x?
10. What is Tcl?
11. What is a servlet engine/container?
12. What is BIND?
13. Name the steps to setup a slave zone in BIND
14. Name the steps to setup a primary zone in BIND
15. What commands would you use under Solaris or Linux to modify/view an LDAP tree?

Windows Server and MS Exchange interview questions

1. What is DHCP? How we configure DHCP?
2. What are the ways to configure DNS & Zones?
3. What are the types of backup? Explain each?
4. What are Levels of RAID 0, 1, 5? Which one is better & why?
5. What are FMSO Roles? List them.
6. Describe the lease process of the DHCP server.
7. Disaster Recovery Plan?
8. What is scope & super scope?
9. Differences between Win 2000 Server & Advanced Server?
10. Logical Diagram of Active Directory? What is the difference between child domain & additional domain server?
11. FTP, NNTP, SMTP, KERBEROS, DNS, DHCP, POP3 port numbers?
12. What is Kerberos? Which version is currently used by Windows? How does Kerberos work?

Microsoft Exchange Server interview questions

1. Distribution List?
2. GAL, Routing Group, Stm files, Eseutil & ininteg - what are they used for?
3. What is MIME & MAPI?
4. List the services of Exchange Server 2000?
5. How would you recover Exchange server when the log file is corrupted?

Network engineer interview questions

1. User(s) are complaining of delays when using the network. What would you do?
2. What are some of the problems associated with operating a switched LAN?
3. Name some of the ways of combining TCP/IP traffic and SNA traffic over the same link.
4. What sort of cabling is suitable for Fast Ethernet protocols?
5. What is a Class D IP address?
6. Why do I sometimes lose a server’s address when using more than one server?
7. What is Firewall?
8. How do I monitor the activity of sockets?
9. How would I put my socket in non-blocking mode?
10. What are RAW sockets?
11. What is the role of TCP protocol and IP protocol.
12. What is UDP?
13. How can I make my server a daemon?
14. How should I choose a port number for my server?
15. Layers in TCP/IP
16. How can I be sure that a UDP message is received?
17. How to get IP header of a UDP message
18. Writing UDP/SOCK_DGRAM applications
19. How many bytes in an IPX network address?
20. What is the difference between MUTEX and Semaphore?
21. What is priority inversion?
22. Different Solutions to dining philosophers problem.
23. What is a message queue?
24. Questions on Shared Memory.
25. What is DHCP?
26. Working of ping, telnet, gopher.
27. Can I connect two computers to internet using same line ?

Network developer interview questions

1. How does TCP handshake work?
2. How does SSL handshake work?
3. What is the difference between passive FTP and active FTP?
4. What is the difference between socket and session?
5. How does network management station work?
6. What are the different phases in VPN establishment?
7. How does DH (deffie helman) work?
8. What is TCP window sizing?
9. What is MTU?

Some PC and networking questions

1. Workers can not print from the printer, there user log on are correct and are allowed to print from that printer in active directory. How would you resolve this issue?
2. What is the difference between hub and switch?
3. Your hard drive is partitioned as follows: 8 gigs for OS drive C, 8 gigs for Hot Swappable dirve D and rest is free as dirve E. Your drive C crashes, how would you reboot your system without installing a new operating system?
4. Your computer gives you “non-disk error” before you log on what would you do to make your computer work?

General Java Servlet questions

1. What is the servlet?
2. What are the JSP atrributes?
3. What is the need of super.init(config) in servlets?
4. How to know whether we have to use jsp or servlet in our project?
5. Can we call destroy() method on servlets from service method?
6. What is the Servlet Interface?
7. What is the difference between GenericServlet and HttpServlet?
8. How we can check in particular page the session will be alive or not?
9. What is the importance of deployment descriptor in servlet?
10. When we increase the buffer size in our project using page directive attribute ‘buffer’ what changes we observe?
11. What is the difference between ServetConfig and ServletContext..?
12. When a servlet accepts a call from a client, it receives two objects. What are they?
13. What are the differences between GET and POST service methods?
14. In which conditions we have to use the ServletContext?
15. What methods will be called in which order?((i.e)service(),doget(),dopost())
16. Servlet is Java class. Then why there is no constructor in Servlet? Can we write the constructor in Servlet
17. What is the use of ServletConfig and ServletContext..?
18. What information that the ServletRequest interface allows the servlet access to?
19. What is the difference between ServletContext and ServletConfig?
20. When do you have action=get?
21. What is a Singleton class. How do you write it?
22. What is difference between sendRedirect() and forward()..? Which one is faster then other and which works on server?
23. What information that the ServletResponse interface gives the servlet methods for replying to the client?
24. Can I invoke a JSP error page from a servlet?
25. Can a init(ServletConfig config) method be overrided in servlets?
26. How many ServletConfig and servlet context objects are present in one application?
27. Do we have a constructor in servlet? can we explictly provide a constructor in servlet programme as in java program?
28. What are the uses of Servlets?
29. Can I just abort processing a JSP?
30. Is servlet is used to create a dynamic webpage or Static webpage or both?
31. If you want a servlet to take the same action for both GET and POST request, what should you do?
32. What is the difference between JSP and SERVLETS?
33. What are the advantages using servlets than using CGI?
34. What is a better approach for enabling thread-safe servlets and JSPs? SingleThreadModel Interface or synchronization?
35. We have two applications in that we have two servlets each.How they(servlets) communicate with each other?
36. How the server will know (i.e) when it can invoke init, service,destroy methods of servlet life cycle?
37. How to communicate between two servlets?
38. What is the difference between servlets and applets?
39. How will u pass the argument from one servlet to another servlet?
40. What method used to add a jsp to the servlet?
41. How HTTP Servlet handles client requests?
42. How to get one Servlet’s Context Information in another Servlet?
43. Difference between single thread and multi thread model servlet
44. What is the super class of All servlets?
45. How are Servlet Applet communication achieved?
46. What is servlet context and what it takes actually as parameters?
47. What is the servlet life cycle?
48. Types of Servlets?
49. Why is that we deploy servlets in a webserver.What exactly is a webserver?
50. Which code line must be set before any of the lines that use the PrintWriter?

Windows sysadmin interview questions

1. What is Active Directory schema?
2. What are the domain functional level in Windows Server 2003?
3. What are the forest functional level in Windows Server 2003?
4. What is global catalog server?
5. How we can raise domain functional & forest functional level in Windows Server 2003?
6. Which is the deafult protocol used in directory services?
7. What is IPv6?
8. What is the default domain functional level in Windows Server 2003?
9. What are the physical & logical components of ADS
10. In which domain functional level, we can rename domain name?
11. What is multimaster replication?
12. What is a site?
13. Which is the command used to remove active directory from a domain controler?
14. How we can create console, which contain schema?
15. What is trust?
16. What is the file that’s responsible for keep all Active Directory database?