May 28, 2011

ARP (Address Resolution Protocol)

It help ip network devices find other device on the same segment or Vlan |ـــــ ARP uses a local broad cast to discover neighboring device |ـــــ ARP resolves ip addresses to mac addresses so that machines on the same data link layer media can communicate with each other.

Protocol                                                                                   Protocol ID
Internet Control Message Protocol (ICMP)                                          1
Transmission Control Protocol (TCP)                                                  6
Interior Gateway Routing Protocol (IGRP)                                          9
User Datagram Protocol (UDP)                                                           17
Internet Protocol version 6 (IPv6)                                                       41
Internet-work Packet Exchange (IPX)                                                    111

Internet Control Message Protocol (ICMP)

  • It is used to send error & control information between ip network devices.
  • There are many diffident messages that can be shared, including the following: 
1. Echo request: Determines whether on ip node ( a host or a router is available on network.)
2. Echo Reply: Replies to ICMP echo request.
3. Destination Unreachable: Informs the host that a datagram can't be delivered.
4. Source Quench: Informs the host to lower the rate at which it sends datagram because of congestion.
5. Redirect: Informs the host of a preferred rate.
6. Time Exceeded: Indicate that the TTL of IP datagram has expired.

May 21, 2011

What is Datagram?

A datagram is a basic transfer unit associated with a packet-switched network in which the delivery arrival time and order are not guaranteed. A datagram consists of header and data areas, where the header contains information sufficient for routing from the originating equipment to the destination without relying on prior exchanges between the equipment and the network. The source and destination addresses as well as a type field are found in the header of a datagram.

May 14, 2011

Do you want to have FREEDOM ?

Publisher: Hall PTR
Language: English
ISBN: 0132435942
Paperback: 448 pages
Data: August 11, 2006
Format: PDF
Publisher: Apress
Language: English
ISBN: 1590596277
Paperback: 608 pages
Data: March 15, 2006

May 13, 2011

Using the Pipe

 It is the output modifier. This pipe ( | ) allow us to wade through all the configurations or other long out puts & get straight to our goods fast.

Arman#sh run | ?
Append Append redirected out put to URL ( URLs supporting append operation only )
Begin Begin with the line that matches.

May 7, 2011

Setting up SSH

Which creates a more secure session than the Telnet app that use an uncrypted data stream.
Here are the steps to setting up SSH:
1. Set your host name:
Router(config)#host name Rezakhani

2. Set the domain name (both the host name & domain name are required for the encryption keys to be generated) :
Rezakhani(config)# ip domain -name

3. Generate the encryption keys for security the session:
 Rezakhani(config)# crypto key generate rsa  general -keys modulus ?
<360-2048> size of the key modulus [360-2048]
Rezakhani(config)# crypto key generate rsa general -keys modulus 1024

- The name for keys will be
- % The key modulus size is 1024 bits

Do command

** Beginning with IOS version 12.3
  • Cisco has finally added a command to the IOS that always you to view the configuration & statics from within configuration mode.
 ** In fact with a pre -12.3 router,

  • you'd get the following error if you tried to view the configuration from global - Config
you see:

Router (config)# sh run

% invalid input detected at  ' ^ '  marker
  • Compare that to the output i got from entering that same command on my router that's running the 12.4 IOS
Enter configuration commands, one per line. End with CNTL/Z

May 6, 2011


you can see it, HERE

  • Rout able: it can pass through routers.
  • Connect dissimilar systems: Win, Mac, Unix, etc...
  • Method of access to the inventor. 
App Layer: using an app, it gains access to the network.
Transportation: provides communication sessions between the two computers.  TCP, UDP
Internet Layer: routers the data from it's source to it's source to its destination.   ARP, RARP, IP, ICMP, IGMP.
Network Layer: it sends & receive data on the wire.  Ethernet, Token Ring, Frame, Relay, ATM 

(Well-Know Port Numbers:
FTP: 20 & 21, SMTP: 25,  DNS: 53, Telnet:23, HTTP: 80, HTTPS: 443)

May 4, 2011

Subneting class c addresses **Normal Way!**

Before i start this article  i should say don't worry if you can't understanding it! you can see the fast way!

- In class C address, only 8 bits are available for defining the hosts.
- Remember that subnet bits start at the left & go to the right without skipping bits.
- This means that the only class C subnet mask can be following.

Binary                    Decimal                    CIDR
00000000                    0                              /24
10000000                    128                          /25
11000000                    192                          /26
11100000                    224                          /27

** We can't use /31 or /32 because we have to at least 2 host bits for assigning IP address to hosts

Robots & Transportation Network

فیلم ساخت و عملکرد یک شبکه حمل و نقل اتوماتیک به وسیله لگو و ربات‌های مختلف

Construction methods and performance of a transportation network  by automated   various robots

May 2, 2011

نکاتی‌ در مورد امنیت شبکه (PERSIAN)

امنیت شبکه یکی‌ از مورد بسیار بسیار مهم می‌باشد که جا دارد به آن پرداخته شود.
وقتی‌ که از امنیت شبکه صحبت می‌کنیم شامل مورد بسیار زیادی میشود که هر کدام از آنها به تنهای میتواند مورد بحث قرار گیرد،همیشه در امنیت شبکه موضوی که بسیار اهمیت دارد لایه‌های دفأعی یک شبکه می‌باشد، باید یاد آوری کرد که اولین لایه دفأعی در امنیت شبکه و حتا امنیت فیزیکی‌ وجود یک ساختار و خط مشی‌ (policy) می‌باشد که بدون آن ،لیست کنترل ، فایروال و هر لایه دیگری بدون معنی می‌باشد دقیقا مثل ساختمانی می‌باشد که پایه ندارد !

May 1, 2011

VLAN Video Learning (ENGLISH)


How to create Subnets

To create subnetworks you take bits from the host portion of the ip address & reserve them to define the subnet address.
This means fewer bits for hosts, so the more subnets the fewer bits available for defining hosts.

IP Subnet-Zero

This command allows you to use first & last subnet in your network design.
The class C mask of 192 provides subnets 64 & 128.
BUT with the ip subnet-zero command, you now get to use subnets 0 , 64, 128 & 192.
* that is two more subnets for every subnet mask use.