Config. Router2 (24/1/08 Khamis)

Config. Router1 (24/1/08 Khamis)

Subnet Mask

Defination :

subnet mask is a screen of numbers used for routing traffic within a subnet. Once a packet has arrived at an organization's gateway or connection point with its unique network number, it can be routed to its destination within the organization's internal gateways using the subnet number.

The subnet mask consists of a screen of numbers indicating to the router which numbers it should look at underneath. In a binary mask, for example, a "1" over a number says "Look at the number underneath;" a "0" says "Don't look." Using a mask saves the router having to handle the entire 32 bit address; it can simply look at the bits selected by the mask.

Using the previous example (which is a very typical case), the combined network number and subnet number occupy 24 bits or three of the quads. The appropriate subnet mask carried along with the packet would be: 255.255.255.0

Or a string of all 1's for the first three quads (telling the router to look at these) and 0's for the host number (which the router doesn't need to look at). Subnet masking allows routers to move the packets on more quickly.

If you have the job of creating subnets for an organization (an activity called subnetting) and specifying subnet masks, your job may be simple or complicated depending on the size and complexity of your organization and other factors.

Reference - http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci1248394,00.html

Ping

Defination :

Ping is a basic Internet program that allows a user to verify that a particular IP address exists and can accept requests. The verb ping means the act of using the ping utility or command. Ping is used diagnostically to ensure that a host computer you are trying to reach is actually operating. If, for example, a user can't ping a host, then the user will be unable to use the File Transfer Protocol (FTP) to send files to that host. Ping can also be used with a host that is operating to see how long it takes to get a response back. Using ping, you can learn the number form of the IP address from the symbolic domain name (see "Tip").

Loosely, ping means "to get the attention of" or "to check for the presence of" another party online. Ping operates by sending a packet to a designated address and waiting for a response. The computer acronym (for Packet Internet or Inter-Network Groper) was contrived to match the submariners' term for the sound of a returned sonar pulse.
Ping can also refer to the process of sending a message to all the members of a mailing list requesting an ACK (acknowledgement code). This is done before sending e-mail in order to confirm that all of the addresses are reachable.

Reference - http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214297,00.html

ipconfig/all = utk melihat ip address, subnet mask, gateway, DNS1,DNS2.

IP : 10.1.0.55

SM : 255.255.0.0

Gateway Default : 10.1.0.4

DNS1 : 202.188.0.132

DNS2 : 202.188.0.133

CISCO Router - 22/1/08 (Selasa)

ROUTER
1 device utk mhubkn 2 network segment yg berbeza.

Cara berfungsi :
· Router akn extract paket yg diterima kpd destinasinya (destinasi ttentu kpd tuan punya paket).
· Akn memilih laluan terbaik bg paket & 4ward paket tsbt di spjng laluan yg dah dipilih.
· Terima, control, select de path & pilih de best router atr 2 network wlpun terdpt byk network.

Definition router

A device that routes data between networks using IP addressing. Routers provide firewall security.

A device or setup that finds the best route between any two networks, even if there are several networks to traverse. Like bridges, remote sites can be connected using routers over dedicated or switched lines to create WANs.

The hardware or software that handles connection between networks online. In other words, it tells your computer where to go.

A router is a computer networking device that buffers and forwards data packets across an internetwork toward their destinations, through a process known as routing. Routing occurs at layer 3 (the Network layer e.g. IP) of the OSI seven-layer protocol stack.

A network device that transmits message packets, routing them over the best route available at the time. Routers are used to connect multiple network segments, including those based on differing architectures and protocols.

Ip Address-latihan 16/1/08 (Rabu)

Router

Definition: Routers are physical devices that join multiple wired or wireless networks together. Technically, a wired or wireless router is a Layer 3 gateway, meaning that the wired/wireless router connects networks (as gateways do), and that the router operates at the network layer of the OSI model.
Home networkers often use an Internet Protocol (IP) wired or wireless router, IP being the most common OSI network layer protocol. An IP router such as a DSL or cable modem broadband router joins the home's local area network (LAN) to the wide-area network (WAN) of the Internet.
By maintaining configuration information in a piece of storage called the "routing table," wired or wireless routers also have the ability to filter traffic, either incoming or outgoing, based on the IP addresses of senders and receivers.
Some routers allow the home networker to update the routing table from a Web browser interface. Broadband routers combine the functions of a router with those of a network switch and a firewall in a single unit.
Reference - http://compnetworking.about.com/cs/routers/g/bldef_router.htm

DHCP

Definition: DHCP allows a computer to join an IP-based network without having a pre-configured IP address. DHCP is a protocol that assigns unique IP addresses to devices, then releases and renews these addresses as devices leave and re-join the network.
Internet Service Providers (ISPs) usually use DHCP to allow customers to join the Internet with minimum effort. Likewise, home network equipment like broadband routers offers DHCP support for added convenience in joining home computers to the LAN.
DHCP environments require a DHCP server set up with the appropriate configuration parameters for the given network. Key DHCP parameters include the range or "pool" of available IP addresses, the correct subnet masks, plus gateway and name server addresses.
Devices running DHCP client software can then automatically retrieve these settings from DHCP servers as needed. Using DHCP on a network means system administrators do not need to configure these parameters individually for each client device.
Reference -http://compnetworking.about.com/cs/protocolsdhcp/

DHCP is a key technology that broadband routers, Internet connection sharing software like Microsoft ICS, and corporate proxy servers all rely on.
Reference - http://compnetworking.about.com/b/2004/01/18/what-is-dhcp.htm

The Dynamic Host Configuration Protocol (DHCP) supports automatic address assignment and improved configuration management of IP networks.
Reference -http://compnetworking.about.com/cs/protocolsdhcp/

Subnet

Defination :
A subnet (short for "subnetwork") is an identifiably separate part of an organization's network. Typically, a subnet may represent all the machines at one geographic location, in one building, or on the same local area network (LAN). Having an organization's network divided into subnets allows it to be connected to the Internet with a single shared network address.

Without subnets, an organization could get multiple connections to the Internet, one for each of its physically separate subnetworks, but this would require an unnecessary use of the limited number of network numbers the Internet has to assign. It would also require that Internet routing tables on gateways outside the organization would need to know about and have to manage routing that could and should be handled within an organization.
The Internet is a collection of networks whose users communicate with each other.

Each communication carries the address of the source and destination networks and the particular machine within the network associated with the user or host computer at each end. This address is called the IP address (Internet Protocol address). This 32-bit IP address has two parts: one part identifies the network (with the network number) and the other part identifies the specific machine or host within the network (with the host number). An organization can use some of the bits in the machine or host part of the address to identify a specific subnet. Effectively, the IP address then contains three parts: the network number, the subnet number, and the machine number.
The standard procedure for creating and identifying subnets is provided in Internet Request for Comments 950.

The 32-bit IP address is often depicted as a dot address (also called dotted quad notation) - that is, four groups (or quads) of decimal numbers separated by periods. Here's an example: 130.5.5.25

Each of the decimal numbers represents a string of eight binary digits. Thus, the above IP address really is this string of 0s and 1s:

10000010.00000101.00000101.00011001

As you can see, we inserted periods between each eight-digit sequence just as we did for the decimal version of the IP address. Obviously, the decimal version of the IP address is easier to read and that's the form most commonly used.

Some portion of the IP address represents the network number or address and some portion represents the local machine address (also known as the host number or address). IP addresses can be one of several classes, each determining how many bits represent the network number and how many represent the host number. The most common class used by large organizations (Class B) allows 16 bits for the network number and 16 for the host number. Using the above example, here's how the IP address is divided:
<--Network address--><--Host address-->
130.5 . 5.25

If you wanted to add subnetting to this address, then some portion (in this example, eight bits) of the host address could be used for a subnet address. Thus: <--Network address--><--Subnet address--><--Host address-->
130.5 . 5 . 25

To simplify this explanation, we've divided the subnet into a neat eight bits but an organization could choose some other scheme using only part of the third quad or even part of the fourth quad.
Once a packet has arrived at an organization's gateway or connection point with its unique network number, it can be routed within the organization's internal gateways using the subnet number. The router knows which bits to look at (and which not to look at) by looking at a subnet mask, which is a screen of numbers that tells you which numbers to look at underneath. In a binary mask, a "1" over a number says "Look at the number underneath"; a "0" says "Don't look." Using a mask saves the router having to handle the entire 32 bit address; it can simply look at the bits selected by the mask.

Reference - http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci213065,00.html

Ip Address

Sebagai pengenalan bagi sesebuah komputer/host.
Ip address adalah berpandukan kepada Class A,B atau C.
Class A : 11111111 00000000 00000000 00000000
255 0 0 0
Class B : 11111111 111111111 00000000 00000000
255 255 0 0
Class C : 11111111 111111111 11111111 11111111
255 255 255 0

Class B & C selalu digunakan dan Class A jarang digunakan.

10.1.0.x-----------> ip address bg anggaran pc/host mencecah ribu
192.168.1.x-------> " ratusan & kebawah.
202.188.0.133---->segment 202 adalah kepunyaan TMnet.
Bagi mengurangkan kadar traffic line(talian sibuk) maka perlu block ip address fail-fail exe.,download,movie,audio @ lain2 yg selalu dilawati. [Bagi mana2 student IPT/KISMEC :) ]

An IP address (Internet Protocol address) is a unique address that certain electronic devices currently use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP)—in simpler terms, a computer address.

Any participating network device—including routers, switches, computers, infrastructure servers (e.g., NTP, DNS, DHCP, SNMP, etc.), printers, Internet fax machines, and some telephones—can have its own address that is unique within the scope of the specific network.

Some IP addresses are intended to be unique within the scope of the global Internet, while others need to be unique only within the scope of an enterprise.

The IP address acts as a locator for one IP device to find another and interact with it. It is not intended, however, to act as an identifier that always uniquely identifies a particular device. In current practice, an IP address is not always a unique identifier, due to technologies such as dynamic assignment and network address translation.

Reference - http://en.wikipedia.org/wiki/Ip_address

Definition of: static IP address (Ip yang disetkan oleh administrator)

A permanent numeric identification assigned by the network administrator to a node in a TCP/IP network. Static IP addresses are used for shared resources such as Web servers and Webcams.

ISPs assign static IP addresses to the Internet connections of their large business customers, which command a premium over dynamic IP addresses. Contrast with dynamic IP address. See IP address.


Definition of: dynamic IP address (Ip yang diberi @ disetkan oleh modem.)
A temporary numeric identification assigned to a node in a TCP/IP network. When computers and devices in the network are turned on, they are assigned an IP address by a DHCP server.

ISPs typically assign dynamic addresses to the Internet connections of their residential and small business customers, which are less expensive than static addresses. That means the IP address to the outside world in a cable or DSL modem may change every month, every day or even every hour (see DDNS). Contrast with static IP address. See IP address and DHCP.

3 step Chipping (Julius Caeser)

In cryptography, a Caesar cipher, also known as a Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a shift of 3, A would be replaced by D, B would become E, and so on. The method is named after Julius Caesar, who used it to communicate with his generals.

The encryption step performed by a Caesar cipher is often incorporated as part of more complex schemes, such as the Vigenère cipher, and still has modern application in the ROT13 system. As with all single alphabet substitution ciphers, the Caesar cipher is easily broken and in practice offers essentially no communication security.




Example
The transformation can be represented by aligning two alphabets; the cipher alphabet is the plain alphabet rotated left or right by some number of positions. For instance, here is a Caesar cipher using a left rotation of three places (the shift parameter, here 3, is used as the key):

Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Cipher: DEFGHIJKLMNOPQRSTUVWXYZABC


Reference - http://en.wikipedia.org/wiki/Caesar_cipher


Contoh Cryptography ciptaan sendiri :

NETWORK SECURITY

Kursus : INSEP (SKIM INDUSTRIAL SKILLS ENHANCEMENT PROGRAM) - NETWORK SECURITY PROFESIONAL
Tempoh : 6 bulan [ 4 bulan Off the Job + 2 bulan On the Job)
Elaun : RM500
Alamat : KISMEC - Kedah Industrial Skills and Management Development Centre126,
Jln PKNK 1/1,Kawasan Perusahaan Sungai Petani,
08000 Sungai Petani,Kedah Darul Aman.

Tel : 604-4414619 / 604-4414621
Fax : 604-4414622 / 604-4427653

Tenaga Pengajar :
En Kamal

Pn. Munirah (Pembantu)

Erti rangkaian

SEBUAH sistem rangkaian komputer membabitkan dua buah komputer yangdihubungkan dengan media menggunakan talian terus atau talian telefon.

Manakala sistem rangkaian yang rumit atau kompleks bergantung kepada imaginasi masing-masing. Rangkaian komputer bermaksud semua nod seperti pelayan, stesen kerja, pencetak dan sebagainya dihubungkan diantara satusama lain dengan tujuan untuk berkongsi maklumat dan bahan.Sebarang maklumat yang adapada pihak A dapat disebarkan kepada pengguna lain dan pihak A juga dapat menerima maklumat dari pihak atau pengguna lain.


Rujukan - www.komputer.com.my/artikel/15032002.txt


Keselamatan Rangkaian Keselamatan

Secara umumnya adalah kombinasi semua mekanisma yang membenarkan orang-orang tertentu sahaja menggunakan sumber yang diingini. Manakala keselamatan komputer adalah penggunaan katalaluan(password) yang hanya membenarkan orang tertentu sahaja yang menggunakan. Terdapat juga satu konsep yang dinamakan keselamatan perimeter iaitu, sebelum sesorang itu dibenarkan masuk ke rangkaian dalaman untuk mencapai sumber komputer, maka mereka haruslah perkenalkan diri kepada peranti keselamatan perimeter seperti firewall atau modem katalaluan.

Rujukan - http://209.85.175.104/search?q=cache:0XCQoCjf_S0J:www.geocities.com/akramicro/tutorial/Firewall2.doc+%22maksud+keselamatan+rangkaian%22%2B%22komputer%22&hl=en&ct=clnk&cd=1&gl=my


Network security

Consists of the provisions made in an underlying computer network infrastructure, policies adopted by the network administrator to protect the network and the network-accessible resources from unauthorized access and the effectiveness (or lack) of these measures combined together.


Comparison with computer securitySecuring network infrastructure is like securing possible entry points of attacks on a country by deploying appropriate defense. Computer security is more like providing means of self-defense to each individual citizen of the country. The former is better and practical to protect the civilians from getting exposed to the attacks. The preventive measures attempt to secure the access to individual computers--the network itself--thereby protecting the computers and other shared resources such as printers, network-attached storage connected by the network. Attacks could be stopped at their entry points before they spread. As opposed to this, in computer security the measures taken are focused on securing individual computer hosts. A computer host whose security is compromised is likely to infect other hosts connected to a potentially unsecured network. A computer host's security is vulnerable to users with higher access privileges to those hosts.


Rujukan - http://en.wikipedia.org/wiki/Network_security