Monday, December 7, 2015
Explain the OSPF, Open Shortest Path First. What are the different areas in OSPF?
Explain the OSPF, Open Shortest Path First. What are the different areas in OSPF?
OSPF is a protocol for routing to be used in IP networks. It is a link-state routing protocol and is a part of interior gateway protocols group. It operates in a single autonomous system. OSPF is most widely used interior gateway protocol.The areas are as follows:
Backbone area
Backbone is also referred as ‘area 0’ or ‘area 0.0.0.0’. It is the core of an OSPF network and all other areas are connected to it. Inter-area routing happens through routers that are connected to the backbone area and their associated areas.
Stub area
The external route advertisements are not received by the stub area. Many route advertisements are configured into an area. This occurs at the time where the routing table consists of mostly external routes. It is advised to have a default route to the stub area. Stub area will have only one OSPF router.
Not-so-stubby area
A stub area which can import autonomous system external routes and send them to other areas is known as Not-so-stubby area. NSSA is an extension of stub area which allows external routes injection in a limited fashion into the stub area.
What are NETBIOS and NETBEUI?
What are NETBIOS and NETBEUI?
Network Basic Input Output System provides session layer of OSI model related services which allows the applications on different computers for communicating over a LAN. NetBIOS runs over TCP/IP through NetBIOS over TCP/IP (NBT) protocol. This process results in every computer in the network with NetBIOS name and an IP address that corresponds to a host name.NetBIOS Extended User Interface is an extended version of NetBIOS. It is a program that allows computers to communicate within a local area network. NetBEUI forms the frame format which was not a specification of NetBIOS. NetBEUI is the best choice for performing communication within a LAN.
Difference between bit rate and baud rate?
Difference between bit rate and baud rate.
The differences between bit rate and baud rate:- Bit rate is measured as number of data bits transmitted / second in communication channel.
- Baud rate is measured as number of times a signal state is changed in a communication channel.
One change of state can transmit one bit or less than one bit which depends on modulation technique used. The bit and baud rate have the connection:
bps = baud / second x the number of bits / per baud
Explain the core naming mechanism, Domain Name System (DNS).?
Explain the core naming mechanism, Domain Name System (DNS).
A Domain Name system is used to convert the names of the website on the internet to IP addresses. The domain names for each IP addresses are stored in a database that is distributed across different servers. A domain name space consists of a tree of domain names. The tree has zones. Zones consist of a collection of connected nodes. These nodes are served by a name server. A domain name is usually in the form of mydomain.com. Here, .com is the top level domain. Where as mydomain is the sub domain or subdivision. A host name is a domain name that has one or more IP addresses associated with it.Explain the functionality of PING?
Explain the functionality of PING.
Ping Is particularly used to check if the system is in network or not. It also gives packet lost information. In windows ping command is written as ping ip_address. The output returns the data packets information. The number of packets sent, received and lost is returned by PING.What is static and dynamic routing? Explain their differences.?
What is static and dynamic routing? Explain their differences.
In static routing the routes are described by fixed paths through a data network. The routes are entered by system administrator. The whole network can be configured by using static routes.Dynamic routing protocols are the applications which discover network destinations dynamically. Routers will communicate the adjacent routers which informs the network to which each router is connected. These routers adjusts automatically in a network when traffic changes.
Differences between static routing and dynamic routing:
Static Routing:
- Manually set up route.
- Stable. No impact of traffic and transmission failures
Dynamic Routing:
- Route setting is automatic
- Responds to the changes of the network
- Optimized route is selected automatically.
Explain the concepts and capabilities of Routing Table.?
Explain the concepts and capabilities of Routing Table.
The information about the data packets route over an Internet Protocol will be determined in a table called routing table as a set of rules. Routers and switches use routing tables.Routing tables contain information for the purpose of forwarding a packet on a path towards its destination. The packet contains the origin and destination information. A network device examines the packets and matches it to the routing table where the destination is available. Then the table provides the device for transmitting the packet to the next hop across the network.
Explain the difference between Broadcast and Multicast.?
Explain the difference between Broadcast and Multicast.
Broadcast : Every device on the network will receive the transmitted packets.Multicast : The data will be delivered to a destinations group simultaneously using most efficient strategy for delivering the messages over a network only once. The copies of the data will be created when the links to the destinations split.
Explain the concept of EIGRP(Enhanced interior gateway routing protocol).?
Explain the concept of EIGRP(Enhanced interior gateway routing protocol).
Interior Gateway Routing Protocol is the proprietary protocol developed by CISCO for addressing the issues associated with routing in large and heterogeneous networks. The vector algorithm and distance information are the same as in Interior Gateway Routing Protocol, EIGRP enhanced for use with more advanced features for avoiding routing loops and speedup the time for convergence. EIGRP transmits the subnet mask for each routing entry by which EIGRP’s VLSM and route summarization is enabled.Explain the concepts of IGRP(Interior gateway protocol). Explain how it works?
Explain the concepts of IGRP(Interior gateway protocol). Explain how it works
Interior Gateway Routing Protocol is the proprietary protocol developed by CISCO for addressing the issues associated with routing in large and heterogeneous networks. Bandwidth, reliability, delay, maximum packet size and load are factors for calculating routing metric using mathematical formula. The smallest calculated metric is considered as the least-cost path. Split horizons and hold-downs concepts are implemented for addressing looping loop issues.Explain the concept of RIP protocol.?
Explain the concept of RIP protocol.
Routing Information Protocol is widely used protocol for the purpose of managing router information within a self containing network such as LAN. A gateway host with a router sends the entire routing table to its closest neighbor host every 30 seconds using RIP. The information will be passed by the neighbor host on to its next neighbor and so on. This process continues until all hosts of the network have the same knowledge of the routing paths, called as network convergence. The network distance is determined by using a ‘hop’ count. For routing a packet to the next host for a specified destination, routing table information is used.Distance Vector vs. Link-State Protocol.
Distance Vector vs. Link-State Protocol.
Distance Vector Protocol:- Each router in the protocol sends information about destination and next hop to reach there, to its neighbor routers
- The routes will be installed directly in the tables.
Link-State Protocol:
- The links attached to the routers and the state of these links are sends by each router
- The protocol is available through out the network
- The router’s table is calculated by individual routers.
Explain Interior and Exterior Routing Protocols.?
Explain Interior and Exterior Routing Protocols.
Autonomous system’s routing is handled by Interior Gateway Protocols. Switching from places to places between the routers, figure out. The protocols are utilized to keep track of getting between destinations to other side of a network or to administrate the networks. These protocols perform the communication between networks.What is Routing Protocol? Explain its purposes.?
What is Routing Protocol? Explain its purposes.
- Routing protocol specifies how the routers communicate, disseminating the information which enables the routers to be selected between two nodes in a network.- Routing protocol interacts and informs the hardware that is needed to transmit the data between transmitter and the receiver for transmission over network.
Explain the concept of Collision Domain. Explain why collisions occur in HUBS and Repeaters.?
Explain the concept of Collision Domain. Explain why collisions occur in HUBS and Repeaters.
If two computer systems transmit at the same time a collision occurs. The collision with CSMA/CD network is known as Collision Domain.In an Ethernet network a group of nodes compete with each other for access. If two or more devices transmit at the same time, a collision occurs. Each transmitting-receiving pair of nodes in a switched Ethernet environment has its own collision domain.
While sending the data packets through every other port, a collision occurs.
What is NAT? Explain how NAT actually works?
What is NAT? Explain how NAT actually works.
Network Address Translation is the full form of NAT. It is a technology that is commonly used for IP translation and mapping. It allows sharing internet access to home networkers. NAT implements the accessibility by using a device or software which allows the entire home network to share internet access.NAT acts as interface between the private network (home users network) and the public network (internet). NAT is available between the internet and the home network. When a request is sent from a private network to the public network, a little conduit will be opened by the NAT device between the home computer and the destination computer. The response sent by public network system will be sent back to the client though NAT.
What is multicasting?
What is multicasting?
Multicasting allows a single message to be sent to a group of recipients. Emailing, teleconferencing, are examples of multicasting. It uses the network infrastructure and standards to send messages.How would you define IP address?
How would you define IP address?
IP address or Internet Protocol address is the address of a device attached to an IP network (TCP/IP network). It is a must for every client, server and network device to have a unique IP address for each network connection (network interface). Every IP packet contains a source IP address and a destination IP address. As a device moves from one network to another, its IP address changes.Computers using the TCP/IP for communication are uniquely identified by a 32 bit address called as an IP address. The routers use the IP address information to forward the packet to the destination computer.
IP addresses are categorized as:
- Private address: these IP addresses are used exclusively within a private network and not for public to see.
- Public Address: these are registered IP addresses used for public.
Each IP address has a network address and a host address. IP addresses are expressed in four sets of three numbers, separated with dots. Each set is called as an octet because when converted to binary; it denotes eight binary.
What is MAC address?
What is MAC address?
Media Access Control address is an identifier for assigned to most network adapters or Network Interface Cards by the manufacturer for the purpose of identification. MAC address is used in MAC protocol sub layer. MAC address is usually encodes the registered identification number that is registered by the manufacturer. The numbering spaces managed by the IEEE, which are common for formulating a MAC address: MAC-48, EUI-48 and EUI-64.Explain IP, TCP and UDP?
Explain IP, TCP and UDP.
TCP – Transmission control Protocol is used to establish communication between nodes or networks and exchange data packets. It guarantees delivery of data packets in the order they were sent. Hence it is most commonly used in all applications that require guaranteed delivery of data. It can handle both timeouts (if packets were delayed) and retransmission (if packets were lost). The stream of data is transmitted in segments. The segment header is 32 bit. it is a connectionless communication protocol at the third level (network) of the OSI model.IP – Internet protocol is used for transmission of data over the internet. IP uses IP addresses to identity each machine uniquely. Message is sent using small packets. The packet contains both the sender and receivers address. IP does not guarantee the delivery in the same order as sent. This is because the packets are sent via different routes. It is a connectionless communication protocol at the third level (network) of the OSI model.
UDP – User Data Protocol is a communication protocol. It is normally used as an alternative for TCP/IP. However there are a number of differences between them. UDP does not divide data into packets. Also, UDP does not send data packets in sequence. Hence, the application program must ensure the sequencing. UDP uses port numbers to distinguish user requests. It also has a checksum capability to verify the data.
What are network topologies? Explain Ring, Bus and Star topology?
What are network topologies? Explain Ring, Bus and Star topology.
A network topology describes the layout of a network. It describes how different nodes and elements are connected to each other. Different types of topology:1. Ring:-
a. All nodes connected with another in a loop.
b. Each device is connected to one or more another device on either side.
2. Bus
a. All nodes connected to a central and a common cable called as a back bone.
b. In bus topology, the server is at one end and the clients are connected at different positions across the network.
c. Easy to manage and install.
d. If the backbone fails, the entire communication fails.
3. Star
a. All nodes connected to a central hub.
b. The communication between the nodes is through the hub.
c. Relative requires more cables as compared to BUS. However if any node fails, it wont affect the entire LAN.
What is a network? What are the different kinds of network? Explain them?
What is a network? What are the different kinds of network? Explain them
A network is a group of computers or nodes connected together. They are connected with each other by communication paths.Types of Networks:
LAN – Local Area Network connects a group of nodes covering a small physical area. LAN’s are most commonly seen in offices, building etc. LAN’s enable higher transfer rate of data, smaller coverage of area and hence less wiring.
WAN – Wide Area Network connects a group of nodes covering a wide area. WAN typically connects and allow communication between regions or national boundaries. The most common example of WAN is internet.
VPN – Virtual Private Network connects or links nodes in some larger area by open connections or virtual circuits in some larger network (e.g., the Internet) instead of by physical wires. It is used for secure communication through the public internet. VPN alone may not support explicit security features, such as authentication or content encryption.
Intranet – It is a set of networks under the control of a single administrative person. It can be considered as an internal network of an organization. If it is large, web servers are used to provide information to the users.
Extranet – It is a network that restricts itself within a single organization. It can be categorized as WAN, MAN etc. however; it cannot have a single LAN. It must have a connection (at least one) with external network.
Explain the 7 Layers of OSI?
Explain the 7 Layers of OSI.
Layer 1: Physical layerIt represents all the electrical and physical specifications for devices.
Layer 2: Data link layer
It provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the Physical layer.
Layer 3: Network layer
The Network layer provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks.
Layer 4: Transport layer
It provides transparent transfer of data between end users.
Layer 5: Session layer
It controls the sessions between computers. It connects, manages and terminates the connections between the local and remote application.
Layer 6: Presentation layer
It transforms data to provide a standard interface for the Application layer.
Layer 7: Application layer
It provides a means for the user to access information on the network through an application.
Define File Transfer Protocol?
Define File Transfer Protocol.
File Transfer Protocol (FTP), a standard Internet protocol, is the simplest way to exchange files between computers on the Internet. Like the Hypertext Transfer Protocol (HTTP), which transfers displayable Web pages and related files, and the Simple Mail Transfer Protocol (SMTP), which transfers e-mail, FTP is an application protocol that uses the Internet's TCP/IP protocols. FTP is commonly used to transfer Web page files from their creator to the computer that acts as their server for everyone on the Internet. It's also commonly used to download programs and other files to your computer from other servers.What is FTP (File Transfer Protocol)?
FTP is File Transfer Protocol. It used to exchange files on the internet. To enable the data transfer FTP uses TCP/IP, FTP is most commonly used to upload and download files from the internet. FTP can be invoked from the command prompt or some graphical user interface. FTP also allows to update (delete, rename, move, and copy) files at a server. It uses a reserved port no 21.What is Groupware server?
What is Groupware server?
Groupware server is software that allows the collaboration of users, irrespective of location through the internet or intranet to work together in an atmosphere which is virtual.Define the term Protocol?
Define the term Protocol.Protocol is a standard way of communicating across a network. A protocol is the "language" of the network. It is a method by which two dissimilar systems can communicate. TCP is a protocol which runs over a network. |
What's the difference Between an Intranet and the Internet?
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What are TP-Lite and TP-Heavy Monitors?
What are TP-Lite and TP-Heavy Monitors?
- TP-Lite Monitor: The integration of TP monitors functions in a database engines is called as TP-Lite monitor.- TP-Heavy Monitor: A TP monitor that supports the client/server architecture and allows PC for initiating very complex multiserver transaction from the desktop.
What is Message Oriented Middleware (MOM)?
What is Message Oriented Middleware (MOM)?
An infrastructure focuses on sending and receiving messages to increment interoperability, flexibility and flexibility of an application. MOM performs this by allowing an application to be distributed over platforms of different kind. MOM reduces the application development complexity which spans multiple operating systems and network protocols. This process insulates the application developer from the operating systems details and network interfaces. Various APIs across diverse platforms and networks are provided by MOM.What is a Transaction server?
What is a Transaction server?
- A transaction server is software that is used for implementing transactions.- A transaction comprises of multiple steps that must automatically be completed
- A transaction server consists of a safety providing system and environment where the programs can be written for making use of the features of guaranteed transactions.
What is the difference between POP3 and IMAP Mail Server?
What is the difference
between POP3 and IMAP Mail Server?
POP3:
- All emails are to be downloaded again if used by another desktop PC for checking the email.
- May lead to confusion if used for checking email in office and at home PC.
- Attachments will be down loaded into desktop while the ‘check new email’ process is in progress.
- Mailboxes can be created only on desktop and one mail box exists on the server.
IMAP:
- There is no need for downloading all email while using another desktop PC for checking email.
- Unread mail identification is easier.
- Message downloading is possible only when opened for display from its contents.
- Multiple mailboxes creation is possible on the desktop PC and also on the server.
- All emails are to be downloaded again if used by another desktop PC for checking the email.
- May lead to confusion if used for checking email in office and at home PC.
- Attachments will be down loaded into desktop while the ‘check new email’ process is in progress.
- Mailboxes can be created only on desktop and one mail box exists on the server.
IMAP:
- There is no need for downloading all email while using another desktop PC for checking email.
- Unread mail identification is easier.
- Message downloading is possible only when opened for display from its contents.
- Multiple mailboxes creation is possible on the desktop PC and also on the server.
Difference between ARP and RARP?
Difference between ARP
and RARP.
- Address Resolution Protocol is utilized for mapping IP network address to the hardware address that uses data link protocol.
- Reverse Address Resolution Protocol is a protocol using which a physical machine in a LAN could request to find its IP address from ARP table or cache from a gateway server.
- IP address of destination to physical address conversion is done by ARP, by broadcasting in LAN.
- Physical address of source to IP address conversion is done by RARP.
- ARP associates 32 bit IP address with 48 bit physical address.
- Allowing a host to discover its internet address after knowing only its physical address is done by RARP
Top 50 Shell script interview?
1: What is a shell?
Shell is a interface between user and the kernel. Even though there can be only one kernel ; a system can have many shell running simultaneously . Whenever a user enters a command through keyboard the shell communicates with the kernel to execute it and then display the output to the user.
2: What are the different types of commonly used shells on a typical linux system?
csh,ksh,bash,Bourne . The most commonly used and advanced shell used today is “Bash” .
3:What is the equivalent of a file shortcut that we have on window on a Linux system?
Shortcuts are created using “links” on Linux. There are two types of links that can be used namely “soft link” and “hard link”
4:What is the difference between soft and hard links?
Shell Scripting
Soft links are link to the file name and can reside on different filesytem as well; however hard links are link to the inode of the file and has to be on the same filesytem as that of the file. Deleting the orginal file makes the soft link inactive (broken link) but does not affect the hard link (Hard link will still access a copy of the file)
5: How will you pass and access arguments to a script in Linux?
Arguments can be passed as:
scriptName “Arg1” “Arg2”….”Argn” and can be accessed inside the script as $1 , $2 .. $n
6: What is the significance of $#?
$# shows the count of the arguments passed to the script.
7: What is the difference between $* and $@?
$@ treats each quoted arguments as separate arguments but $* will consider the entire set of positional parameters as a single string.
8: Use sed command to replace the content of the file (emulate tac command)
Eg:
Then O/p should be
EFGH
ABCD
ABCD
Here G command appends to the pattern space,
h command copies pattern buffer to hold buffer
and d command deletes the current pattern space.
9: Given a file, replace all occurrence of word “ABC” with “DEF” from 5th line till end in only those lines that contains word “MNO”
10: Given a file , write a command sequence to find the count of each word.
”(backslash)011” is octal equivalent of “tab character” and
“(backslash)012” is octal equivalent of newline character.
11: How will you find the 99th line of a file using only tail and head command?
tail +99 file1|head -1
12: Print the 10th line without using tail and head command.
13:In my bash shell I want my prompt to be of format ‘$”Present working directory”:”hostname”> and load a file containing a list of user defined functions as soon as I login , how will you automate this?
In bash shell we can create “.profile” file which automatically gets invoked as soon as I login and write the following syntax into it.
Here File1 is the file containing the user defined functions and “.” invokes this file in current shell.
14: Explain about “s” permission bit in a file?
“s” bit is called “set user id” (SUID) bit.
“s” bit on a file causes the process to have the privileges of the owner of the file during the instance of the program.
Eg: Executing “passwd” command to change current password causes the user to writes its new password to shadow file even though it has “root” as its owner.
15: I want to create a directory such that anyone in the group can create a file and access any person’s file in it but none should be able to delete a file other than the one created by himself.
We can create the directory giving read and execute access to everyone in the group and setting its sticky bit “t” on as follows:
16: How can you find out how long the system has been running?
Command “uptime”
17: How can any user find out all information about a specific user like his default shell, real life name, default directory,when and how long he has been using the sytem?
finger “loginName” …where loginName is the login name of the
user whose information is expected.
18: What is the difference between $$ and $!?
$$ gives the process id of the currently executing process whereas $! shows the process id of the process that recently went into background.
19: What are zombie processes?
These are the processes which have died but whose exit status is still not picked by the parent process. These processes even if not functional still have its process id entry in the process table.
20: How will you copy file from one machine to other?
We can use utilities like “ftp” ,”scp” or “rsync” to copy file from one machine to other.
Eg: Using ftp:
ftp hostname
>put file1
>bye
Above copies file file1 from local system to destination system whose hostname is specified.
21: I want to monitor a continuously updating log file, what command can be used to most efficiently achieve this?
We can use tail –f filename . This will cause only the default last 10 lines to be displayed on std o/p which continuously shows the updating part of the file.
22: I want to connect to a remote server and execute some commands, how can I achieve this?
We can use telnet to do this:
telnet hostname –l user
>Enter password
>Write the command to execute
>quit
23: I have 2 files and I want to print the records which are common to both.
We can use “comm” command as follows:
comm -12 file1 file2 … 12 will suppress the content which are
unique to 1st and 2nd file respectively.
24: Write a script to print the first 10 elemenst of Fibonacci series.
25: How will you connect to a database server from linux?
We can use isql utility that comes with open client driver as follows:
isql –S serverName –U username –P password
26: What are the 3 standard streams in Linux?
0 – Standard Input
1 – Standard Output
2 – Standard Error
1 – Standard Output
2 – Standard Error
27: I want to read all input to the command from file1 direct all output to file2 and error to file 3, how can I achieve this?
command <file1 1>file2 2>file3
28: What will happen to my current process when I execute a command using exec?
“exec” overlays the newly forked process on the current process ; so when I execute the command using exec, the command gets executed on the current shell without creating any new processes.
Eg: Executing “exec ls” on command prompt will execute ls and once ls exits, the process will shut down
29: How will you emulate wc –l using awk?
awk ‘END {print NR} fileName’
30: Given a file find the count of lines containing word “ABC”.
grep –c “ABC” file1
31: What is the difference between grep and egrep?
egrep is Extended grep that supports added grep features like “+” (1 or more occurrence of previous character),”?”(0 or 1 occurrence of previous character) and “|” (alternate matching)
32: How will you print the login names of all users on a system?
/etc/shadow file has all the users listed.
awk –F ‘:’ ‘{print $1} /etc/shadow’|uniq -u
33: How to set an array in Linux?
Syntax in ksh:
Set –A arrayname= (element1 element2 ….. element)
In bash
A=(element1 element2 element3 …. elementn)
34: Write down the syntax of “for “ loop
Syntax:
for iterator in (elements)
do
execute commands
done
35:How will you find the total disk space used by a specific user?
du -s /home/user1 ….where user1 is the user for whom the total disk
space needs to be found.
36: Write the syntax for “if” conditionals in linux?
Syntax
If condition is successful
then
execute commands
else
execute commands
fi
37:What is the significance of $? ?
$? gives the exit status of the last command that was executed.
38: How do we delete all blank lines in a file?
where (backslash)011 is octal equivalent of space and
(backslash)040 is octal equivalent of tab
39: How will I insert a line “ABCDEF” at every 100th line of a file?
sed ‘100i\ABCDEF’ file1
40: Write a command sequence to find all the files modified in less than 2 days and print the record count of each.
find . –mtime -2 –exec wc –l {} \;
41: How can I set the default rwx permission to all users on every file which is created in the current shell?
We can use:
This will set default rwx permission for every file which is created to every user.
42: How can we find the process name from its process id?
We can use “ps –p ProcessId”
43: What are the four fundamental components of every file system on linux?
bootblock, super block, inode block and datablock
44: What is a boot block?
This block contains a small program called “Master Boot record”(MBR) which loads the kernel during system boot up.
45: What is a super block?
Super block contains all the information about the file system like size of file system, block size used by it,number of free data blocks and list of free inodes and data blocks.
46: What is an inode block?
This block contains the inode for every file of the file system along with all the file attributes except its name.
47: How can I send a mail with a compressed file as an attachment?
zip file1.zip file1|mailx –s “subject” Recepients email id
Email content
EOF
48: How do we create command aliases in shell?
alias Aliasname=”Command whose alias is to be created”
49: What are “c” and “b” permission fields of a file?
“c “ and “b” permission fields are generally associated with a device file. It specifies whether a file is a character special file or a block special file.
50: What is the use of a shebang line?
Shebang line at top of each script determines the location of the engine which is to be used in order to execute the script.
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