What is V-model- advantages, disadvantages and when to use it?

What is V-model- advantages, disadvantages and when to use it?

V- model means Verification and Validation model. Just like the waterfall model, the V-Shaped life cycle is a sequential path of execution of processes. Each phase must be completed before the next phase begins.  Testing of the product is planned in parallel with a corresponding phase of development.

The various phases of the V-model are as follows:

Requirements like BRS and SRS begin the life cycle model just like the waterfall model. But, in this model before development is started, a system test plan is created.  The test plan focuses on meeting the functionality specified in the requirements gathering.

The high-level design (HLD) phase focuses on system architecture and design. It provide overview of solution, platform, system, product and service/process. An integration test plan is created in this phase as well in order to test the pieces of the software systems ability to work together.

The low-level design (LLD) phase is where the actual software components are designed. It defines the actual logic for each and every component of the system. Class diagram with all the methods and relation between classes comes under LLD. Component tests are created in this phase as well.

The implementation phase is, again, where all coding takes place. Once coding is complete, the path of execution continues up the right side of the V where the test plans developed earlier are now put to use.

Coding: This is at the bottom of the V-Shape model. Module design is converted into code by developers.

Advantages of V-model:

    Simple and easy to use.
    Testing activities like planning, test designing happens well before coding. This saves a lot of time. Hence higher chance of success over the waterfall model.
    Proactive defect tracking – that is defects are found at early stage.
    Avoids the downward flow of the defects.
    Works well for small projects where requirements are easily understood.

Disadvantages of V-model:

    Very rigid and least flexible.
    Software is developed during the implementation phase, so no early prototypes of the software are produced.
    If any changes happen in midway, then the test documents along with requirement documents has to be updated.

When to use the V-model:

    The V-shaped model should be used for small to medium sized projects where requirements are clearly defined and fixed.
    The V-Shaped model should be chosen when ample technical resources are available with needed technical expertise.

High confidence of customer is required for choosing the V-Shaped model approach. Since, no prototypes are produced, there is a very high risk involved in meeting customer expectations.
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 System Requirements Specification (SyRS):

A System Requirements Specification (abbreviated SyRS when need to be distinct from a Software Requirements Specification SRS) is a structured collection of information that embodies the requirements of a system.

A business analyst, sometimes titled system analyst, is responsible for analyzing the business needs of their clients and stakeholders to help identify business problems and propose solutions. Within the systems development life cycle domain, the BA typically performs a liaison function between the business side of an enterprise and the information technology department or external service providers.

Software requirements specification

A software requirements specification (SRS) is a description of a software system to be developed, laying out functional and non-functional requirements. (Non-functional requirements impose constraints on the design or implementation such as performance engineering requirements, quality standards, or design constraints.) The specification may include a set of use cases that describe interactions the users will have with the software.

SDLC, Software Development Life Cycle

SDLC, Software Development Life Cycle

SDLC Overview

SDLC, Software Development Life Cycle is a process used by software industry to design, develop and test high quality softwares. The SDLC aims to produce a high quality software that meets or exceeds customer expectations, reaches completion within times and cost estimates.

• SDLC is the acronym of Software Development Life Cycle.
• It is also called as Software development process.
• The software development life cycle (SDLC) is a framework defining tasks performed at each step in the software development process.
• ISO/IEC 12207 is an international standard for software life-cycle processes. It aims to be the standard that defines all the tasks required for developing and maintaining software.

A typical Software Development life cycle consists of the following stages:

• Stage 1: Planning and Requirement Analysis
• Stage 2: Defining Requirements
• Stage 3: Designing the product architecture
• Stage 4: Building or Developing the Product
• Stage 5: Testing the Product
• Stage 6: Deployment in the Market and Maintenance

SDLC Models
There are various software development life cycle models defined and designed which are
followed during software development process. These models are also referred as "Software
Development Process M
odels". Each process model follows a Series of steps unique to its type,
in order to ensure success in process of software development. Following are the most
important and popular SDLC models followed in the industry:

Waterfall Model

Iterative Model

Spiral Model

V-Model

Big Bang Model The other related methodologies are Agile Model, RAD Model
–
Rapid Application : Development and Prototyping Models



Waterfall Model
The Waterfall Model was first Process Model to be introduced. It is also referred to as
a linear - sequential life cycle model. It is very simple to understand and use.
In a waterfall model, each phase must be completed before the next phase can begin and there
is no overlapping in the phases. Waterfall model is the earliest SDLC approach that was used for software development .
The waterfall Model illustrates the software development process in a linear sequential flow; hence it is also referred to as a linear - sequential life cycle model. This means that any phase in
the development process begins only if the previous phase is complete.
In waterfall model phases do not overlap. .
Waterfall Model design Waterfall approach was first SDLC Model to be used widely in
Software Engineering to ensure success of the project.
In "The Waterfall" approach, the whole process of software development is divided into separate
phases. In Waterfall model, typically, the outcome of one phase acts as the input for the next phase sequentially.

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Iterative model :

Advantages of Iterative model:

    In iterative model we can only create a high-level design of the application before we actually begin to build the product and define the design solution for the entire product. Later on we can design and built a skeleton version of that, and then evolved the design based on what had been built.
    In iterative model we are building and improving the product step by step. Hence we can track the defects at early stages. This avoids the downward flow of the defects.
    In iterative model we can get the reliable user feedback. When presenting sketches and blueprints of the product to users for their feedback, we are effectively asking them to imagine how the product will work.
    In iterative model less time is spent on documenting and more time is given for designing.

 Disadvantages of Iterative model:

    Each phase of an iteration is rigid with no overlaps
    Costly system architecture or design issues may arise because not all requirements are gathered up front for the entire lifecycle

When to use iterative model:

    Requirements of the complete system are clearly defined and understood.
    When the project is big.
    Major requirements must be defined; however, some details can evolve with time.

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Spiral Model :-

The spiral model is similar to the incremental model, with more emphasis placed on risk analysis. The spiral model has four phases: Planning, Risk Analysis, Engineering and Evaluation. A software project repeatedly passes through these phases in iterations (called Spirals in this model). The baseline spiral, starting in the planning phase, requirements are gathered and risk is assessed. Each subsequent spirals builds on the baseline spiral.

Planning Phase: Requirements are gathered during the planning phase. Requirements like ‘BRS’ that is ‘Bussiness Requirement Specifications’ and ‘SRS’ that is ‘System Requirement specifications’.

Risk Analysis: In the risk analysis phase, a process is undertaken to identify risk and alternate solutions.  A prototype is produced at the end of the risk analysis phase. If any risk is found during the risk analysis then alternate solutions are suggested and implemented.

Engineering Phase: In this phase software is developed, along with testing at the end of the phase. Hence in this phase the development and testing is done.

Evaluation phase: This phase allows the customer to evaluate the output of the project to date before the project continues to the next spiral.

Advantages of Spiral model:

    High amount of risk analysis hence, avoidance of Risk is enhanced.
    Good for large and mission-critical projects.
    Strong approval and documentation control.
    Additional Functionality can be added at a later date.
    Software is produced early in the software life cycle.

Disadvantages of Spiral model:

    Can be a costly model to use.
    Risk analysis requires highly specific expertise.
    Project’s success is highly dependent on the risk analysis phase.
    Doesn’t work well for smaller projects.

 When to use Spiral model:

    When costs and risk evaluation is important
    For medium to high-risk projects
    Long-term project commitment unwise because of potential changes to economic priorities
    Users are unsure of their needs
    Requirements are complex
    New product line
    Significant changes are expected (research and exploration)

ccna teacher

IP Address Classes
Class A 1 – 127 (Network 127 is reserved for loopback and internal testing)
Leading bit pattern 0
00000000.00000000.00000000.00000000
Class B 128 – 191 Leading bit pattern 10
10000000.00000000.00000000.00000000
Class C 192 – 223 Leading bit pattern 110
11000000.00000000.00000000.00000000
Class D 224 – 239 (Reserved for multicast)
Class E 240 – 255 (Reserved for experimental, used for research)


Private Address Space
Class A 10.0.0.0 to 10.255.255.255
Class B 172.16.0.0 to 172.31.255.255
Class C 192.168.0.0 to 192.168.255.255

Default Subnet Masks
Class A
255.0.0.0
Class B
255.255.0.0
Class C
255.255.255.0


2n where N is the number of bits in the subnet mask. IE, 2^4 = 4 bits of host space = 16 host addresses, minus 2, an address for the "network" and an address for being on a multiaccess network (broadcast address).

Example... 192.168.1.16/28 (32 minus the number of bits = 28). So, you have 2^N hosts, which means you have 192.168.1.16, .17, .18...29,.30,.31,.32 but, you loose the all 0's bits (0000) and the all ones (1111) as these have a significance. The 0000s would be 192.168.1.16 (the network address) and the 1111 would be the broadcast address, which would be 192.168.1.31
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Dear There are two sub-layers in Data link Layer that is Mac layer and Logical link layer.MAC defines how packets are placed on the media. LLC is responsible for identifying Network Layer protocols and encapsulating them..LLC header tells the data link layer,what to do with a packet once a frame is received.

data packets are placed on the media by encoding ...

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What is a Network Switch: Unmanaged Switches

An unmanaged switch works right out of the box. It's not designed to be configured, so you don't have to worry about installing or setting it up correctly. Unmanaged switches have less network capacity than managed switches. You'll usually find unmanaged switches in home networking equipment.
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What is a Network Switch?

To understand basic networking, you first need to answer the question, "What is a network switch?"

Most business networks today use switches to connect computers, printers and servers within a building or campus. A switch serves as a controller, enabling networked devices to talk to each other efficiently. Through information sharing and resource allocation, switches save businesses money and increase employee productivity.
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CCNA Teacher

CCNA Teacher


If we create LOOPBACK address we are not giving no shutdown because we are creating logical interface, in switching if we create int vlan (for ex int van2,van3)this is also logically creating then why we need to give NOSHUTDOWN???????????

All IP interfaces are down by default. This is to allow you to add and move subnets without risk of propagating routes or creating an overlap. Loopbacks are a special case as they don't have an L2 component. It makes little sense for it to be up by default, but meh...

concept of loopback was mainly developed for testing purpose. hence they are up by default n order to save our time .but on vlans scenario is different intrface are logical but placed on physical
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 In STP why priority is giving multiple of 4096??????????

 It is because in the days of plain old vanilla STP we had 2 bytes for the bridge priority 0 - 65535 ( in math we inc the zero, so 65536 variations). But when RSTP came along we needed a vlan id field - that took 12 bits leaving only 4 bits for bridge priority.

4 bits have 16 possible variations, so 16 * 4096 = 65536
Very good question
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what is the difference between the root port and designated port ?

There can be ONLY one Root Port on a switch. There may be multiple Designated Ports on a switch

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Hi Community,
I am setting up a lab at the office to start studying by myself, I have SWs 2x3560 2x3550 3x2900, routers will be in GNS3, and to access the SWs I have a 2511 with 16 async interfaces.
I am trying to connect to any of the SWs with no joy.

Here's what I am doing: I already have all my SWs configured with the basic commands, they are all up and running. The 2511 is configured as follows:
line con 0
line 1 16
transport input all
exec-timeout 0 0
no exec
session-timeout 20
int loopback0
ip add 1.1.1.1 255.255.255.255
ip host C13560 2001 1.1.1.1
.
.
.
.
ip host A32900 2007 1.1.1.1
When issuing in exec mode
#1
or
‪#‎telnet‬ 1.1.1.1 2001
I get an unreachable host error message
Note: I am using the proper cable to connect from the async interface to the console port on the SW.
I wonder if any of you guys could help a little bit.

  ---
 Aux would go to a gateway to access the 2511 remotely. This particular 2511 doesn't have the interface to connect the octal cable, it has 16 Async interfaces, which go to every console ports of your devices

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An IP address can be divided in two parts, network bits 'x' and host bits 'y'. To obtain the number of usable IPs in a network do (2^y)-2. You remove 2 from the count since the IPs are in use for other reasons: one of them is the network boundary and the other is the broadcast.

In any network, there is a limited number of IP addresses that can be assigned to hosts on the network. This is the formula. Take for example the network 192.168.1.0/24. You have 32 bits total, or four octets of 8 bits, but 24 are network bits and can't be assigned to hosts. The last 8 bits are the host bits. You can't use the zero address, 192.168.1.0 because it belongs to the network itself. You can't use 192.168.1.255 because it is the broadcast address. Anything else from .1 to .254 can be assigned to a host on the network. So 2 raised to the 8th power minus 2 = 254 host addresses available


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Hi Guys,
I want to know what is an Unmanaged Switch? Is it a Hub or not is what I want to know actually.
We know a Hub has one collision and one broadcast domain so let' say if I connect multiple devices to a Hub and if even two of them try to send at the same time there will be a collison causing data corruption etc. Now, if an Unmanaged switch is nothing but a Hub then wouldn't I face the same problem if two or more than two devices try to send or receice at the same time?

Reply : With a hub all workstations are essentially on the same wire and every port sees every packet.
A switch will build mac address tables and forward most traffic intelligently.
So a dumb switch isn't a hub.
I guess you could say the switch, even a toy one, operates more at layer 2 in the OSI model where the hub is purely layer 1.

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Hey Rahul,

An un-managed switch is not an hub. I've a cyber-cafe.... earlier my LAN was built using Hubs, however i've replaced them with un-managed switches.

I see a lot of difference in the speed of my LAN. And i don't think the unmanaged switches maintain a MAC table. I believe the difference between those two is: Hub acts like a bus topology, whereas the un-managed switch acts like a star topology. And even hub operate at 10mbps whereas an un-managed switch can operate between 10-100 mbps. The unmanaged switch helped a lot for me to enhance my cafe..

While using hubs the video streaming was very slow it is used to stop for every few mins then again buffer like this... but now there is no latency at all using unmanageble switches.

Please don't forget to rate the helpful posts.

Regards,
Chandu
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Alain Cadet 7 months ago

Hi,

And i don't think the unmanaged switches maintain a MAC table

That would mean they would flood all the time so basically act like hubs and in this case I don't think you would have seen a performance increase in your network
Regards
Alain
Don't forget to rate helpful posts.

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As they are unmanaged , no you can't view the MAC table but if they flood everything you will see it by sniffing on another PC linked to the switch, if it doesn't flood unicast you'll only see unknown unicast frames but not known unicast frames.

Regards

Alain
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David :

An unmanaged switch is just that, unmanaged.
Its still a switch in that it maintains a MAC addresss table and forwards frames based on this.
A hub and an unmanaged switch are not the same thing.

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Joseph : An unmanaged switch is one you cannot configure (i.e. you cannot manage it, ergo its unmanaged).  It is not a hub.  BTW, there are (or were) manageable hubs.

PING SOCKET

PING SOCKET


Ping is a program using a raw ICMP socket the program is presented with a copy of all incoming ICMP messages .
There are three commonly encountered types of sockets: stream, datagram, and raw.
TCP uses the stream type and UDP uses the datagram type.
Raw sockets are used by any application that needs to interact directly with
IP, bypassing TCP and UDP in doing so.

ICMP is a necessary component of any TCP/IP implementation. It does not exist to provide information to the higher-layer protocols (like TCP and UDP) so that they may be more reliable.

ICMP protocol is in fact an Internet layer protocol (Layer 3) and is an integral part of the IP protocol suite.
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it doesn't necessarily mean that only layer 3 devices like router can work with IP but two PCs directly connected with each other can also communicate based on IP and generate messages. the main responsibility of layer 3 device is to forward your packet to other networks were not reachable within your broadcast domain.
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That's the management IP, used to configure and manage a "managed" switch, without this management IP, you can only configure it through the console port or any other ports. When u ping from the switch, it uses its management IP as src IP, that's why you get the respond even though it's not L3 switch. L2 only means it have functions for packet processing up to L2 e.g. MAC ACL, but you can't do things like IP ACL on L2 switch.

switches r of 2 types manageble(l3) ,unmanageble(l2)..................manageble switch .has al functions of router except routing

Wrong. Even my lowly 1900 switch is both L2 and manageable

SUBNET AND CIDR

SUBNET AND CIDR

7 bit subnet = 10000000=128 /25
6 bit subnet = 11000000=192 /26
5 bit subnet = 11100000=224 /27
4 bit subnet = 11110000=240 /28
3 bit subnet = 11111000=248 /29
2 bit subnet = 11111100=252 /30
1 bit subnet = 11111110=254 /31

Understanding CIDR Subnet Mask Notation

m0n0wall uses a subnet mask format that you may not be familiar with. Rather than the common 255.x.x.x, it uses CIDR (Classless InterDomain Routing) notation.

1.5.1. CIDR Table

You can refer to the following table to find the CIDR equivalent of your subnet mask.

Table 1.1. CIDR Subnet Table

Subnet Mask	CIDR Prefix	Total IP's	Usable IP's	Number of Class C networks
255.255.255.255	/32	1	1	1/256th
255.255.255.254	/31	2	0	1/128th
255.255.255.252	/30	4	2	1/64th
255.255.255.248	/29	8	6	1/32nd
255.255.255.240	/28	16	14	1/16th
255.255.255.224	/27	32	30	1/8th
255.255.255.192	/26	64	62	1/4th
255.255.255.128	/25	128	126	1 half
255.255.255.0	/24	256	254	1
255.255.254.0	/23	512	510	2
255.255.252.0	/22	1024	1022	4
255.255.248.0	/21	2048	2046	8
255.255.240.0	/20	4096	4094	16
255.255.224.0	/19	8192	8190	32
255.255.192.0	/18	16,384	16,382	64
255.255.128.0	/17	32,768	32,766	128
255.255.0.0	/16	65,536	65,534	256
255.254.0.0	/15	131,072	131,070	512
255.252.0.0	/14	262,144	262,142	1024
255.248.0.0	/13	524,288	524,286	2048
255.240.0.0	/12	1,048,576	1,048,574	4096
255.224.0.0	/11	2,097,152	2,097,150	8192
255.192.0.0	/10	4,194,304	4,194,302	16,384
255.128.0.0	/9	8,388,608	8,388,606	32,768
255.0.0.0	/8	16,777,216	16,777,214	65,536
254.0.0.0	/7	33,554,432	33,554,430	131,072
252.0.0.0	/6	67,108,864	67,108,862	262,144
248.0.0.0	/5	134,217,728	134,217,726	1,048,576
240.0.0.0	/4	268,435,456	268,435,454	2,097,152
224.0.0.0	/3	536,870,912	536,870,910	4,194,304
192.0.0.0	/2	1,073,741,824	1,073,741,822	8,388,608
128.0.0.0	/1	2,147,483,648	2,147,483,646	16,777,216
0.0.0.0	/0	4,294,967,296	4,294,967,294	33,554,432

So where do these CIDR numbers come from anyway?

The CIDR number comes from the number of 1's in the subnet mask when converted to binary.
The common subnet mask 255.255.255.0 is 11111111.11111111.11111111.00000000 in binary. This adds up to 24 1's, or /24 (pronounced 'slash twenty four').
A subnet mask of 255.255.255.192 is 11111111.11111111.11111111.11000000 in binary, or 26 1's, hence a /26.
And so on...

Good Information here : http://doc.m0n0.ch/quickstartpc/intro-CIDR.html

QUESTIONS

QUESTIONS

rip aur ospf ke advantage aur nuksan bata diejye anyone

RIP 16 HOP TAK KAAM KARTA HAI , JABKI OSPF AREA NEIGHBOURSHIP LOG NETWORK BASED

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Non-manageble swith can understand ip address...??????

 A layer 2 device has no purpose for a layer 3 address in its normal operation, it works strictly with MAC addresses. So if it were unmanaged, there would be no use for an IP address. A layer 3 device would need some sort of configuration before it could begin routing so I can't envision any L3 switch that is not manageable.

An unmanaged switch is not a box full of wires.

Yes, but all layer 3 switches are manageble. He is asking for non-manageble switches.

un managed switch is just like a hub with addition to storage for mac addres .

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 whats the scope of DATA CENTER today and in the next say 5-10 years ?
ive been told data center industry is limited to limited region of the world, not a worldwide phenomenon (THAT I DONT BELIEVE PERSONALLY) Correct me if im wrong and help ..

Cisco has come out with their ucs systems which can run hundreds of virtual servers off a single server. We also have the cloud phenomenon currently going on. One takes away from needing large data centers, the other promotes having storage centers.. Only time will tell but tech has a way of seeing large things go small and become more efficient... I.e. room size computers and today's desktops... The trend in my eyes is that data centers will become fewer and more specific location based

Subnetting

Subnetting



 What valid host range is the IP address 172.31.238.81/21 part of?

Subnetting Question Two

What is the maximum number of subnets and hosts per subnet achievable from the network 172.27.0.0/28?

Q1/ 172.31.238.0 =network ip , 172.31.238.1 to 172.31.239.254 Valid Host Range & 172.31.239.255 Gateway ip

1) valid host range 172.31.232.1- 172.31.239.254 .... 2) number of subnet 4096 n host per subnet 14

Q2, 172.27.0.0/28 subnet mask 255.255.248.0
You borrowed 12 bits, so you can create 4096 network with 8 host every network.

CCNA Teacher

CCNA Teacher


While configuring NAT on a CISCO router , we use "ip nat inside source" command.I do understand this.But what happens if i use "ip nat outside source" command.What does this command do?

Basically changes the source address of packets that are traveling from the outside to the inside, so the opposite of the inside command. It will also change the destination address of packets going in the opposite direction. I've not personally used it however its use would stem from when inside addresses are overlapping with addresses that are on the outside of your network which comes from for example people using public IP ranges on their internal network which have been assigned for use online somewhere else.


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Please look at this scenario :
In this simple scenario we would like to put an ACL in the router by which just PC1 would be allowed to telnet to the router.
To do this scenario
after creating ACL by these commands :
Router(config)# ip access-list standard amir
Router(config-std-nacl) # 10 permit host 192.168.10.2
then I recall this ACL on the fa0/0 of Router by these commands :
Router(config)# line vty 0 4
Router(config-line) # ip access-class amir in

But after all these commands and using Packet tracer as a simulator software, both of PCs are able to telnet to the router !! it is not supposed that PC0 (192.168.10.1) will be able to telnet the router. So what is the wrong with those commands ?

if I put that ACL on the interface f0/0 instead of line vty, and using these commands :
Router(config)# int f0/0
Router(config-if) # ip access-group amir in

the scenario will work well .
so I don't know the problem is related to my commands or to Packet tracer as a simulator.
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using number instead of name for ACL didn't work out (in fact I had tried that before I wrote this post) , but using "deny any" worked out even for a named ACL. the point is all of these stories and problems just happend in Packet tracer as a simulator , but you won't face any problem with those command by using GNS3 as a emulator.
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 use out at the end of your command .and also first configur telnet in router.then define access list.

It's not a PT bug! It works fine for me without a deny any at the end of the ACL and applied on the vty line with the access-class command. And I know that it worked fine as back as v4 and we are on 6.1.1 now.

what is the function of two sublayer of data link layer

what is the function of two sublayer of data link layer ???

There are two sub-layers in Data link Layer that is Mac layer and Logical link layer.MAC defines how packets are placed on the media. LLC is responsible for identifying Network Layer protocols and encapsulating them..LLC header tells the data link layer,what to do with a packet once a frame is received.

CCNA EXAM PAPER

1. Which of the following descriptions are true regarding the management connections on a Cisco router? (Choose three.)
- They are non-network connections.
They are used to connect the router to the rest of the production network.
They are synchronous serial ports.
- They are used for initial router configuration.
- They are asynchronous serial ports.
They are accessed using their assigned IP address.

2. The console port can be used for which of the following? (Choose three.)
- debugging.
- password recovery.
routing data between networks.
- troubleshooting.
connecting one router to another.

3. Which of the following describes the function of a WAN?
connects peripherals in a single location.
connects multiple networks in a single building.
provides connectivity on a LAN.
- provides connectivity over a large geographic area.

4. An internetwork must include which of the following? (Choose three.)
- switching.
static addressing.
IETF standardization.
- dynamic or static routing.
- consistent end-to-end addressing.

5. ABC Company just purchased three new routers to start their company network. Which items are needed to establish a terminal session between a PC and the router for the initial configuration? (Choose three.)
straight-through cable.
- terminal emulation software.
- rollover cable.
- RJ-45 to DB-9 connector.
V.35 cable.

6.Terminal emulation software, such as HyperTerminal, can be used to configure a router. Which of the following HyperTerminal options shown in the graphic are correctly set to allow configuration of a Cisco router? (Choose three.)
bits per second.
- data bits.
- parity.
- stop bits.
flow control.

7. Which of the following devices are used in the construction of a WAN? (Choose three.)
hubs.
- routers.
- communication servers.
transceivers.
- modems.
multi-port repeaters.

8. Which of the following are functions of RAM? (Choose three.)
contains startup configuration file.
- stores routing table.
- holds fast switching cache.
retains contents when power is removed.
- stores running configuration file.

9. Why is a console connection to a router or switch preferred when troubleshooting? (Choose two.)
can be accessed remotely.
- does not depend on network services.
- displays startup and error messages by default.
does not require special components.

10. Which basic components do a router and a standard desktop PC have in common? (Choose three.)
- CPU.
hard drive.
- input/output interfaces.
keyboard.
monitor.
- system bus.

11. During the initial configuration of a 2600 series Cisco router, which cable is required for connecting a PC to the console port?
twisted.
crossover.
- rollover.
straight.

12. A router is composed of many internal components. Which of the following components stores a copy of the router's configuration file?
metal-oxide memory.
read only memory.
flash memory.
- non-volatile random access memory.

13. What contains the instructions that a router uses to control the flow of traffic through its interfaces?
packet configuration.
- configuration files.
flash memory.
internal components.

14. Several Ethernet hosts on a LAN need the gateway services of a Cisco 2500 series router. Which of the following would be needed to physically connect a router to all of the hosts on the LAN? (Choose two.)
a crossover cable between the transceiver on a router and a switch.
a crossover cables between a switch and hosts on a LAN.
a straight-through cable between the auxiliary port on a router and a switch.
a rollover cable between the console port on a router and a switch.
- straight-through cables between a switch and hosts on a LAN.
- a straight-through cable between the transceiver on a router and a switch.

15. Which router component holds the configuration file when power is lost?
volatile random access memory.
read only memory.
- non-volatile random access memory.
flash memory.

16. Which of the following layers of the OSI model are incorporated in WAN standards? (Choose two.)
- physical layer.
application layer.
transport layer.
- data link layer.
session layer.

17. Which of the following are true regarding router interfaces? (Choose three.)
provide temporary memory for the router configuration files.
- connect the router to the network for packet entry and exit.
- can be on the motherboard or a separate module.
hold the IOS image.
- connect the router to LANs and WANs.

18. Which of the following tasks can be accomplished through a management connection on a router? (Choose three.)
- troubleshooting problems.
- monitoring the system.
capturing LAN data packets.
- configuring the router.
routing data packets.

19. What do routers use to select the best path for outgoing data packets?
ARP tables.
bridging tables.
- routing tables.
switching tables.

20. Which of the following are functions of NVRAM? (Choose two.)
stores the routing table.
- retains contents when power is removed.
- stores the startup configuration file.
contains the running configuration file.
stores the ARP table.

21. Select the statements that correctly describe flash memory in a 2600 series router? (Choose two.)
holds the startup configuration by default.
- can be upgraded with single in-line memory modules.
- stores Cisco IOS software images.
stores routing table information by default.
maintains the only copy of an IOS image after the router is booted.

OSI MODEL

OSI MODEL

The OSI (Open Systems Interconnection) was created by the International Organisation for Standardisation (ISO) as a framework used to describe how data is transferred over a medium from one networked device to another. It is made up of 7 layers:

• 7. Application
• 6. Presentation
• 5. Session
• 4. Transport
• 3. Network
• 2. Data Link
• 1. Physical

The 4 main advantages of the OSI are:

1. It divides the communication process into simpler components, aiding component development, design, and troubleshooting.
2. It encourages industry standardization by defining what functions occur at each layer of the model.
3. It prevents changes in one layer from affecting other layers, so that it does not hamper development.
4. It allows various types of network hardware and software to communicate.

Port & Socket numbers

Port & Socket numbers

A port number is a number that identifies different services that run on a PC or device using TCP or UDP (layer 4), while a socket number is an IP address with the port number included: eg. 192.168.0.10:21

Port numbers are assigned by the IANA (Internet Assigned Numbers Authority)

There a 3 different types of port numbers :
Well known Ports (1 - 1023) - Used for common services such as FTP, HTTP, Telnet, DHCP.
Registered Ports (1024 - 49151) - Used for services that are not as commonly used that they warrant a well known port number. Eg. WAP, MS SQL, World of Warcraft.
Private/Dynamic Ports (49152 - 65535) - Ports that can be used by anyone for any purpose.

You can view ports that are currently being used on your PC by typing 'netstat' into the DOS prompt (as seen below a after colon in private/public address).

What is a socket?
The combination of a source IP address and port number or a destination IP address and port number
the combination of the source and destination sequence numbers and port numbers
the combination of the source and destination sequence and acknowledgment numbers
the combination of the source and destination IP address and source and destination Ethernet address


A TCP socket is an endpoint instance defined by an IP address and a port in the context of either a particular TCP connection or the listening state.
A port is a virtualisation identifier defining a service endpoint (as distinct from a service instance endpoint aka session identifier).
A TCP socket is not a connection, it is the endpoint of a specific connection.
There can be concurrent connections to a service endpoint, because a connection is identified by both its local and remote endpoints, allowing traffic to be routed to a specific service instance.

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