Posts Tagged ‘Networking’

How to configure a switch port to work in Promiscuous mode?

Following are the steps to configure a switch port to work in promiscuous mode.

  1. Connect to console port (using hyper terminal [port com1, speed 9600 bps]).
  2. Run the following commands:

    # configure terminal.

    # no monitor session 1.

    # monitor session 1 source interface fastEthernet 0/1.

    # monitor session 1 destination interface fastEthernet 0/24.

    # encapsulation dot1q.

    # end

    # show monitor session1.


    [Note: Promiscuous mode refers to the special mode of Ethernet hardware, in particular network interface cards (NICs), that allows a NIC to receive all traffic to the network, even if it is not addressed to this NIC. In a wider sense, promiscuous mode also refers to network visibility from a single observation point.]



April 6, 2009 Leave a comment

WiMAX, (802.16e) meaning Worldwide Inter-operability for Microwave Access, is a telecommunications technology that provides wireless transmission of data using a variety of transmission modes, from point-to-multipoint links to portable and fully mobile internet access. The technology provides up to 3 Mbit/s broadband speed without the need for cables. It is a newer standard of wireless networking designed to provide the last mile of high speed internet access to the end user. Some people would call Wimax WiFi on steroids but this would be to broad of an assessment. Wifi was and still will be used in LAN environments for the foreseeable future. WiMax was designed to provide (MAN) Metropolitan Area Access, to homes and businesses.

WiMax base stations will have the ability to provide approximately 60 businesses with T1 access and hundreds of homes with DSL/Cable speed access…in theory. Engineers are stating that WiMax has the capability of reaching 30 Miles but real world testing has shown 4-8 mile working radius. WiMax (MAN) deployments are similar to a WiFi network. First the ISP would have their T3 or higher access. The ISP would then use line of sight antennas (Bridges) to connect to towers that would distribute the non line of sight signal to (MAN) residential/business clients. WiMax line of sight antennas operate at a higher Frequency up to 66mhz. Distribution antennas do not have to be in the line of sight with their clients. Non – line of sight towers operate on a range similar to WiFi . WiMax can operate right next to cell phone towers with no interference. WiMax networks are similar to Wifi in deployment. The Wimax Base station/Tower will beam a signal to a WiMax Receiver. Similar to a WiFi access point sending a signal to a laptop. As far as I can tell laptops will be shipping with Wimax receivers in 2006.


QOS (Quality of Service) is an major issue with WiMax because of the number of people accessing a tower at once. Some would think that a tower could be easily overloaded with a lot of people accessing it at once. Built into the WiMax standard is an algorithm that when the tower/base station is nearing capacity then it automatically will transfer the user to another WiMax tower or cell. Unlike a Wifi clients who have to kind of fight to stay associated with a given access point; WiMax will only have to perform this hand shake at the MAC level the first time they access the network. WiMax is designed for building a network infrastructure when the environment or distance is not favorable to a wired network. Also, WiMax is a cheaper and quicker alternative than having to lay wire. Third world countries will greatly benefit from deploying WiMax networks. WiMax can handle virtually all the same protocols Wifi can including VOIP. African countries are now going to start deploying WiMax networks instead of cell phone networks. Disaster zones can also utilize WiMax giving them the ability to distribute crisis information quickly and cheaply. Militaries are already using wireless technology to connect remote sites. Logistics will be simplified with the ease of tracking with RF technologies. WiMax can also handle Webcams and streaming video which would give commanders eyes on target capability. Just imagine if planes were able to drop preconfigured self deploying WiMax antennas in strategic areas giving troops real time battlefield intel. Armed with wireless cameras, drones and a GPS one soldier would truly be an Army of One.  As WiMax is deployed in more areas theory and real life capabilities of WiMax will come to light. The differences between WiMax and Wifi are simple. Think of a WiMax network as an ISP with out wires, with the signal providing your internet access to your business/ home. Wifi will be used within in your LAN for the near future.


April 3, 2009 1 comment

OSI Reference Model : A networking reference model defined by the ISO (International Organization for Standardization) that divides computer-to-computer communications into seven connected layers. Suchlayers are known as a protocol stack. Each successively higher layer builds on the functions of the layers below, as follows:

  • Application layer :The highest level of the model. It defines the manner in which applications interact with the network, including database management, e-mail, and terminal-emulation programs.
  • Presentation layer : Defines the way in which data is formatted, presented, converted, and encoded.
  • Session layer : Coordinates communications and maintains the session for as long as it is needed, performing security, logging, and administrative functions.
  • Transport layer : Defines protocols for structuring messages and supervises the validity of the transmission by performing some error checking.
  • Network layer : Defines protocols for data routing to ensure that the informationarrives at the correct destination
  •  Data-link layer : Validates the integrity of the flow of data from one node to another by synchronizing blocks of data and controlling the flow of data.
  • Physical layer : Defines the mechanism for communicating with the transmission medium and interface hardware.

Defination of Netwok

Network A group of computers and associated peripheral devices connected by a communications channel capable of sharing files and other resources among several users.A network can range from a peer-to-peer network connecting a small number of users in an office or department, to a LAN connecting many users over permanently installed cables and dial-up lines, to a MAN or WAN connecting users on several networks spread over a wide geographic area.

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