الاثنين، 8 يونيو 2015

Routing 1



at network routing function may be occurred dynamically or statically



Static routing : Static routing occurs when you, the network administrator manually add or   configure routes on each router interface with IP addresses. This is no  simple task, especially when 
you are administering a large network. 


 : In as much as its a complex task, there are benefits of static routes 
 
Bandwidth usage between router is at a minimum, none in some cases.

  There is no overhead on the router CPU.
  It adds security due to choice of route configuration by the administrator.

  It reduces the amount of routes found in the routing table.

  Disadvantages of Static Routes:

Takes too much man hours for configuration especially in a large network.

 Too complex and can sometime be confusing during troubleshooting.


ip route command 
    
          {destination network address} {mask}  {next hop address or exit interface}#



for example

If we need to static route for destination  172.16.10.0 (pc5,pc6,pc7) from source  192.168.30.0 (pc1,pc2.pc3).    What shall I do 

Remember the Static Router command syntax:
Ip route {destination network address} {mask}  {next hop address or exit interface}
 :Static Route configuration on HQ router

HQ(config)#ip route 172.16.10.0 255.255.255.0 se2/0
HQ(config)#interface se2/0
HQ(config-if)#clock rate 64000

-----------------------------------------


 Bandwidth usage between router is at a minimum, none in some cases.
ii.   There is no overhead on the router CPU.
 iii.  It adds security due to choice of route configuration by the administrator.
iv.  It reduces the amount of routes found in the routing table.
Disadvantages of Static Routes:
i.   Takes too much man hours for configuration especially in a large network.
ii.  Too complex and can sometime be confusing during troubleshooting.
              
- See more at: http://orbit-computer-solutions.com/How-to-Configure-Static-Routes.php#sthash.huUJPMcQ.dpufBandwidth usage between router is at a minimum, none in some cases.
ii.   There is no overhead on the router CPU.
 iii.  It adds security due to choice of route configuration by the administrator.
iv.  It reduces the amount of routes found in the routing table.
Disadvantages of Static Routes:
i.   Takes too much man hours for configuration especially in a large network.
ii.  Too complex and can sometime be confusing during troubleshooting.
              
- See more at: http://orbit-computer-solutions.com/How-to-Configure-Static-Routes.php#sthash.huUJPMcQ.dpufBandwidth usage between router is at a minimum, none in some cases.
ii.   There is no overhead on the router CPU.
 iii.  It adds security due to choice of route configuration by the administrator.
iv.  It reduces the amount of routes found in the routing table.
Disadvantages of Static Routes:
i.   Takes too much man hours for configuration especially in a large network.
ii.  Too complex and can sometime be confusing during troubleshooting.
              
- See more at: http://orbit-computer-solutions.com/How-to-Configure-Static-Routes.php#sthash.huUJPMcQ.dpuf

Dynamic routing :  shows how routers can discover this information automatically and share that information with other routers via dynamic routing protocols. A routing protocol is  the language a router speaks with other routers in order to share information about the reach ability and status of networks.


 :  Dynamic routing metrics         

    Hop count:  A hop count metric simply counts router hops
   
 Bandwidth: A bandwidth metric would choose a higher-bandwidth path over a lower-bandwidth link. However, bandwidth by itself still may not be a good metric.
   
Reliability: reliability metrics are based on known qualities of a link as determined by the network administrator. The path with highest reliability would be selected as best.

    Delay: Delay is a measure of the time a packet takes to traverse a route. A routing protocol using delay as a 
metric would choose the path with the least delay as the best path. 

    Load: This metric reflects the amount of traffic utilizing the links along the path. The best path is the one with the lowest load.

   Cost : best path is the lowest cost
  ( cost = FN ( metrics

   Convergence : A dynamic routing protocol must include a set of procedures for a router to inform other routers about its directly connected networks, to receive and process the same information from other routers, and to pass along the information it receives from other routers. Further, a routing protocol must define a metric by which best paths may be determined.

    Load balancing: the practice of distributing traffic among multiple paths to the same destination in order to use bandwidth efficiently. 

show route command 
  
              show ip route #         

Ip route {destination network address} {mask}  {next hop address or exit interface} - See more at: http://orbit-computer-solutions.com/How-to-Configure-Static-Routes.php#sthash.huUJPMcQ.dpuf
   :  Dynamic routing protocols


(Classifying Routing Protocols (3.1.4.1


Routing protocols can be classified into different groups according to their characteristics. Specifically, routing protocols can be classified by their:


  • (Purpose: Interior Gateway Protocol (IGP) or Exterior Gateway Protocol (EGP
  • Operation: Distance vector protocol, link-state protocol, or path-vector protocol
  • Behavior: Classful (legacy) or classless protocol
  • For example, IPv4 routing protocols are classified as follows:
  • RIPv1 (legacy): IGP, distance vector, classful protocol
  • IGRP (legacy): IGP, distance vector, classful protocol developed by Cisco (deprecated from 12.2 IOS and later)
  • RIPv2: IGP, distance vector, classless protocol
  • EIGRP: IGP, distance vector, classless protocol developed by Cisco
  • OSPF: IGP, link-state, classless protocol
  • IS-IS: removed from ccna coursel
  • BGP: removed from ccna course


الجمعة، 5 يونيو 2015

Collision domain and broadcasting

 : Collision domains 
 a part of a network where packet collisions can occur. A collision occurs when two devices send a packet at the same time on the shared network segment. The packets collide and both devices must send the packets again, which reduces network efficiency. Collisions are often in a hub environment, because each port on a hub is in the same collision domain. By contrast, each port on a bridge, a switch or a router is in a separate collision domain.
Router: every port at a router is collision domain.
Switch: every port at a switch is collision domain.
Hub : all is one collision domain

For more examples about collision domain visit

broadcast domain :
A broadcast domain is a logical division of a computer network, in which all nodes can reach each other by broadcast at the data link layer. A broadcast domain can be within the same LAN segment or it can be bridged to other LAN segments. A broadcast domain encompasses a set of devices for  when one of the devices sends a broadcast, all the other devices receive a copy of the broadcast. For example, switches flood broadcasts and multicasts on all ports. Because broadcast frames are sent out all ports, a switch creates a single broadcast domain.

Router: every port at a router is broadcast
Switch: every port at a switch is broadcast

For more examples about collision domain visit

network models 1

network models


(What is OSI (open system interconnection  model

OSI model models created by ISO (international standards organization





 Application
Preparing data & supporting application services

Presentation
Encrypt & decrypt data to be sent across a network

Session
Establish , manage and terminate connections between applications

 Transport
Segmentation data , sequencing , flow control , error detection , error correction and
Acknowledgments  

Network (set ip addressing  and make data segmentation )
Create a logical paths for transmitting data from node to node , including switching , routing , and forwarding .

Datalink
Set  mac addressing and packet data and determine logical link control


Physical :
Conveys the bit stream

network types and topologies


Network types 
:
·         LAN (local area network)
·         MAN (metropolitan area network)
·         WAN (wide area network)



Network topology





network devices

Network Devices





 hubs : A hub serves as a central point to which all of the hosts in a network connect to . 
It receives a signal from one port and sends it out to all other ports. Sometimes it is 
called a multiport repeater .

2-    Switches : Like hubs, a switch is used to connect multiple hosts together, but it has many advantages over a hub. Switch is an OSI Layer 2 device, which means that it can inspect received traffic and make forwarding decisions. Each port on a switch is a separate collision domain and can run in a full duplex mode .

3-    Router  : is a device that routes packets from one network to another. A router is most commonly an OSI Layer 3 device. Routers divide broadcast domains and have traffic filtering capabilities

4-    Bridge :  A device that connects two local-area networks (LANs), or two segments of the same LAN that use the same protocol, such as Ethernet or Token-Ring..



5-    . A firewall is a system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in bothhardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especiallyintranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria .



6-    Access Point :  hardware device or a computer's softwarethat acts as a communication hub for users of a wireless device to connect to a wired LAN. APs are important for providing heightened wireless security and for extending the physical range of service a wireless user has access to.


introduction to ccna



What is a network
 A computer network can be described as a system of interconnected devices that can communicate using some common standard (called protocol). These devices communicate to exchange resources (e.g. files and printers) and services.

Here is an example network consisting of two computers connected together:


What is a protocols ?
In telecommunications, a communication protocol is a system of rules for data exchange within or between computers.

HTTP : (Hypertext Transfer Protocol) is the set of rules for transferring files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. As soon as a Web user opens their Web browser, the user is indirectly making use of HTTP. HTTP is an application protocol that runs on top of the TCP/IP suite of protocols (the foundation protocols for the Internet).