Thursday, September 10, 2009

How To Change Your IP Address

Question: How To Change Your IP Address

With some effort, its possible to change your IP address.

Answer: The procedure depends on whether the IP address is static or dynamic and whether it's public or private.

Changing Public IP Addresses

The IP addresses you use for Internet access are controlled by Internet Service Providers (ISPs). It is not easy to change these, especially if you want to do it quickly.

Some Internet services assign you static IP addresses. To change a static IP address, you will need to contact the ISP and work with their technical support to have them assign a new one.

Most Internet services, however, use dynamic IP addresses via DHCP. The policies of ISPs dictate how to change these. If your computer is directly connected to the Internet, you can attempt to release and renew the address using ipconfig or a similar utility. Consult your ISP technical support for details. Often, you will need to disconnect your modem from the Internet for a long period of time (many hours or a few days) before the ISP will assign a different dynamic IP address.

Changing Private IP Addresses

It is easier to change private IP addresses, the ones used internally on your local network. If using static addressing, you can directly set a new IP address on the device. If using dynamic addresses supplied via a network router, you have a few options:
  • release and renew the DHCP address on the client

  • set up the router (or other DHCP server) to use a different IP address range (and update addressing on the network's other devices accordingly)

  • change one or more devices on the network from dynamic to static addressing. You can mix static and dynamic clients on the same network as long as you avoid using static IP addresses within the numeric range where the DHCP server is likely to issue its addresses.

Why Change Your IP Address?

Some people change a public IP address to avoid online bans. Web site message boards and other services sometimes block individuals by their IP address. Note that some sites block people by their user names, and changing the IP address will have no effect in this case.

Additionally, an ISP may assign you an invalid address due to some technical glitch in their equipment. This is another (more legitimate) reason to change your public IP address.

Changing a private IP address does not at all help with Internet address issues. However, changing these makes sense in a few situations:

  • if you have accidentally configured an invalid address (such as a static IP address in the wrong numeric range)
  • if you are using a malfunctioning router that is providing bad addresses, such as one already being used by another computer on your network
  • if you are installing a new router and re-configuring your home network to use its default IP address range

The choice of IP address does not affect your network performance or network security in any meaningful way.

Sunday, August 30, 2009

What is (Wireless / Computer) Networking?

Question: What is (Wireless / Computer) Networking?

Answer: In the world of computers, networking is the practice of linking two or more computing devices together for the purpose of sharing data. Networks are built with a mix of computer hardware and computer software.

Area Networks

Networks can be categorized in several different ways. One approach defines the type of network according to the geographic area it spans. Local area networks (LANs), for example, typically reach across a single home, whereas wide area networks (WANs), reach across cities, states, or even across the world. The Internet is the world's largest public WAN.

Network Design

Computer networks also differ in their design. The two types of high-level network design are called client-server and peer-to-peer. Client-server networks feature centralized server computers that store email, Web pages, files and or applications. On a peer-to-peer network, conversely, all computers tend to support the same functions. Client-server networks are much more common in business and peer-to-peer networks much more common in homes.

A network topology represents its layout or structure from the point of view of data flow. In so-called bus networks, for example, all of the computers share and communicate across one common conduit, whereas in a star network, all data flows through one centralized device. Common types of network topologies include bus, star, ring and mesh.

Network Protocols

In networking, the communication language used by computer devices is called the protocol. Yet another way to classify computer networks is by the set of protocols they support. Networks often implement multiple protocols to support specific applications. Popular protocols include TCP/IP, the most common protocol found on the Internet and in home networks.

Wired vs Wireless Networking

Many of the same network protocols, like TCP/IP, work in both wired and wireless networks. Networks with Ethernet cables predominated in businesses, schools, and homes for several decades. Recently, however, wireless networking alternatives have emerged as the premier technology for building new computer networks.

Wednesday, August 26, 2009

SRNL, automakers to develop high-performance wireless sensors networks

Several industries use wireless sensors, which can monitor chemical processes or equipment activity and then transmit the data over a wireless network. Still, many facilities that could benefit from the use of wireless sensors must continue to use a wired network instead, because the reliability, speed and security of the current generation of wireless sensors do not meet their needs.

The U.S. Department of Energy's Savannah River National Laboratory and U.S. automakers now have teamed up to develop a new high-performance platform for these sensors that not only serves the industry's needs, but also meets the DOE National Nuclear Security Administration's requirements for security and reliability for use in its facilities.

SRNL has entered into a cooperative research and development agreement with the United States Council for Automotive Research LLC (USCAR), the collaborative automotive technology organization for Chrysler Group LLC, Ford Motor Company and General Motors Corporation. The purpose of the collaboration is to develop a new platform for short range wireless sensors networks that meets the NNSA requirements, and can also be adopted as the industry standard.

Under the agreement, SRNL will develop designs and specifications for the new wireless hardware, then engage a qualified wireless manufacturer to make a prototype, which the partners will test and validate. The ultimate goal of the agreement is to produce a standard for wireless sensor platforms that can be adopted by the International Society of Automation, a global instrumentation, systems and automation standards body.

"As partners with SRNL in this endeavor, we look forward to creating an industry standard for wireless sensor platforms that meets the needs of both industry and government and enables significant cost savings for both," said Don Walkowicz, USCAR executive director. "Traditionally, collaborations between the U.S. automakers and U.S. government laboratories have resulted in innovation and great success."

Both the automotive industry and the NNSA have needs for wireless sensors that are reliable, secure, high speed and able to resist interference from existing systems. This agreement between a DOE laboratory and USCAR to produce a single, agreed-upon platform will broaden the customer base for resulting sensor designs, making it more attractive for developers to design hardware that meets the NNSA requirements.

In the automotive industry, for example, replacing hard-wired body shop robots with wireless-controlled robots would be a prime application area for a new secure, wireless sensor network.

NNSA and its contractors use sensors in their facilities to monitor chemical processes, vibration on large pumps and blowers, and environmental conditions such as shock, vibration, and linear acceleration. The ability to use wireless, rather than wired, sensors, when constructing new facilities or installing new sensors in existing facilities will bring considerable cost savings. NNSA sensors typically exist in gloveboxes or "hot cells," which protect workers from exposure to radioactive or chemical hazards. The cost of running cables in "hot" facilities is more than $2,000 per foot. The electrical/instrument portion of such a facility may have a budget of as much as $400 million; a conservative estimate of the cost savings to use wireless sensors networks has been estimated at $50 million. Existing facilities that are already contaminated would be able to add instrumentation at less than 10% the cost of a wired solution.

"We are pleased to be working with the three U.S. automakers through USCAR to create an industry standard for wireless sensor platforms," said Joe Cordaro, SRNL advisory engineer and former chair of the NNSA Network of Senior Scientists and Engineers, who is serving as SRNL lead for the initiative. "Our common needs will drive a design and framework that are applicable in government and non-government facilities, ultimately providing economies of scale, and ensuring robust and reliable requirements for wireless sensor platforms globally."


SRNL is DOE's applied research and development national laboratory at the Savannah River Site (SRS). SRNL puts science to work to support DOE and the nation in the areas of environmental management, national and homeland security, and energy security. The management and operating contractor for SRS and SRNL is Savannah River Nuclear Solutions, LLC.

Founded in 1992, USCAR is the collaborative automotive technology organization for Chrysler Group LLC, Ford Motor Company and General Motors Corporation. The goal of USCAR is to further strengthen the technology base of the domestic auto industry through cooperative research and development. For more information, visit USCAR's Web site at

Inovonics' wireless sensor network technology available from Norbain

Creating powerful and economical commercial mesh network solutions, Inovonics products include the EchoStream Commercial Mesh Network wireless backbone, intrusion detection systems, smoke detectors, and neck-worn pendant panic buttons and transmitters.

Self-healing and self-configuring, EchoStream Commercial Mesh Networks provide robust wireless coverage for operation in the most challenging of commercial environments. Networks can range from a single panic button, to thousands of sensors, and multiple applications can run on the same wireless backbone serving large multi-site facilities, or anything in between.

The intrusion detection devices can warn of open or broken windows, or doors, and provide accurate motion detection of intruders, while the smoke detectors can also be installed as part of a wireless security system for monitoring by a central station. Unlike standalone smoke detectors, these automatically notify authorities when fire strikes, and provide alerts when maintenance is needed, all via a wireless network. Complementing any mesh network, Inovonics pendant transmitters include water resistant and single or dual button versions, with the ability to send various or multiple alerts.

Steve Thomas, Inovonics' UK regional sales manager added: "Our products feature unparalleled integration to industry-leading control panels. Our relationship with Norbain will build on the synergies of both companies to supply a comprehensive range of great value, innovative security wireless solutions to the commercial installer."

"Inovonics have more than twenty years of specialist experience in the design and development of wireless security applications," says Dave Kelly, Norbain's divisional director of intruder products: "This experience and their solutions are a very welcome addition to the Norbain portfolio."

Tuesday, August 25, 2009

Cisco Network Systems


Cisco network systems solutions help enable anytime, anywhere, secure communications throughout your company and across the Internet. This is achieved by bringing together core networking functions, including routing, switching, security, WAN optimization, and Internet services.

The Cisco network systems end-to-end approach allows technical staff to manage the network centrally. Scalable solutions help businesses incrementally add or upgrade equipment as their needs change.

With proper management, the network reliably connects all local and remote employees and provides them with access to the same business applications and services.

Cisco network systems solutions create an inherently intelligent, integrated network that adapts to current and future business needs by:

  • Providing secure, unconstrained connectivity between employees, customers, and information
  • Delivering quality, real-time applications, such as voice and video, on a converged network platform
  • Helping to ensure access to information and resources from anywhere
  • Automating a manageable and self-defending network
  • Reducing operating expenses
  • Enabling green business, IT, and networking practices

Choosing a systems-based or intelligent network solution provides everything required for secure and comprehensive intranet and Internet services. This approach:

  • Allows networking to transfer individual computer and user security responsibilities to the network itself, centralizing IT security
  • Creates a network that adapts to changing needs
  • Views the network as an orderly, organized system rather than a collection of disparate, individually managed boxes

Intelligent networking solutions for satellite offices tend to be modular. Modularity allows sites to install only desired network features, and simplifies and eases equipment upgrades for changing needs or office expansions.

As an added benefit of this systems-based approach, technical staff at headquarters can centrally manage the network, which keeps staffing counts low while providing reliable service to employees in all locations. By installing a complete networking solution and managing it centrally, you can also better protect valuable business data and guard against viruses, spyware, Internet attacks, and other IT security concerns.

Computer network


The network allows computers to communicate with each other and share resources and information. The Advanced Research Projects Agency (ARPA) designed "Advanced Research Projects Agency Network" (ARPANET) for the United States Department of Defense. It was the first computer network in the world in late 1960s and early 1970s.[1]

Network classification

The following list presents categories used for classifying networks.

Connection method

Computer networks can also be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as Optical fiber, Ethernet, Wireless LAN, HomePNA, Power line communication or Ethernet uses physical wiring to connect devices. Frequently deployed devices include hubs, switches, bridges and/or routers.

Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves or infrared signals as a transmission medium.

ITU-T technology uses existing home wiring (coaxial cable, phone lines and power lines) to create a high-speed (up to 1 Gigabit/s) local area network.

Wired Technologies

Twisted-Pair Wire - This is the most widely used medium for telecommunication. Twisted-pair wires are ordinary telephone wires which consist of two insulated copper wires twisted into pairs and are used for both voice and data transmission. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. The transmission speed range from 2 million bits per second to 100 million bits per second.

Coaxial Cable – These cables are widely used for cable television systems, office buildings, and other worksites for local area networks. The cables consist of copper or aluminum wire wrapped with insulating layer typically of a flexible material with a high dielectric constant, all of which are surrounded by a conductive layer. The layers of insulation help minimize interference and distortion. Transmission speed range from 200 million to more than 500 million bits per second.

Fiber Optics – These cables consist of one or more thin filaments of glass fiber wrapped in a protective layer. It transmits light which can travel over long distance and higher bandwidths. Fiber-optic cables are not affected by electromagnetic radiation. Transmission speed could go up to as high as trillions of bits per second. The speed of fiber optics is hundreds of times faster than coaxial cables and thousands of times faster than twisted-pair wire.

Wireless Technologies

Terrestrial Microwave – Terrestrial microwaves use Earth-based transmitter and receiver. The equipment look similar to satellite dishes. Terrestrial microwaves use low-gigahertz range, which limits all communications to line-of-sight. Path between relay stations spaced approx. 30 miles apart. Microwave antennas are usually placed on top of buildings, towers, hills, and mountain peaks.

Communications Satellites – The satellites use microwave radio as their telecommunications medium which are not deflected by the Earth's atmosphere. The satellites are stationed in space, typically 22,000 miles above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, data, and TV signals.

Cellular and PCS Systems – Use several radio communications technologies. The systems are divided to different geographic area. Each area has low-power transmitter or radio relay antenna device to relay calls from one area to the next area.

Wireless LANs – Wireless local area network use a high-frequency radio technology similar to digital cellular and a low-frequency radio technology. Wireless LANS use spread spectrum technology to enable communication between multiple devices in a limited area. Example of open-standard wireless radio-wave technology is IEEE 802.11b.

Bluetooth – A short range wireless technology. Operate at approx. 1Mbps with range from 10 to 100 meters. Bluetooth is an open wireless protocol for data exchange over short distances.

The Wireless Web – The wireless web refers to the use of the World Wide Web through equipments like cellular phones, pagers, PDAs, and other portable communications devices. The wireless web service offers anytime/anywhere connection.


Networks are often classified as Local Area Network (LAN), Wide Area Network (WAN), Metropolitan Area Network (MAN), Personal Area Network (PAN), Virtual Private Network (VPN), Campus Area Network (CAN), Storage Area Network (SAN), etc. depending on their scale, scope and purpose. Usage, trust levels and access rights often differ between these types of network - for example, LANs tend to be designed for internal use by an organization's internal systems and employees in individual physical locations (such as a building), while WANs may connect physically separate parts of an organization to each other and may include connections to third parties.

Functional relationship (network architecture)

Computer networks may be classified according to the functional relationships which exist among the elements of the network, e.g., Active Networking, Client-server and Peer-to-peer (workgroup) architecture.

Network topology

Computer networks may be classified according to the network topology upon which the network is based, such as bus network, star network, ring network, mesh network, star-bus network, tree or hierarchical topology network. Network topology signifies the way in which devices in the network see their logical relations to one another. The use of the term "logical" here is significant. That is, network topology is independent of the "physical" layout of the network. Even if networked computers are physically placed in a linear arrangement, if they are connected via a hub, the network has a Star topology, rather than a bus topology. In this regard the visual and operational characteristics of a network are distinct; the logical network topology is not necessarily the same as the physical layout. Networks may be classified based on the method of data used to convey the data, these include digital and analog networks.

Types of networks

Below is a list of the most common types of computer networks in order of scale.

Personal area network

A personal area network (PAN) is a computer network used for communication among computer devices close to one person. Some examples of devices that are used in a PAN are printers, fax machines, telephones, PDAs and scanners. The reach of a PAN is typically about 20-30 feet (approximately 6-9 meters), but this is expected to increase with technology improvements.

Local area network

A local area network (LAN) is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport. Current wired LANs are most likely to be based on Ethernet technology, although new standards like ITU-T also provide a way to create a wired LAN using existing home wires (coaxial cables, phone lines and power lines)[2].

For example, a library may have a wired or wireless LAN for users to interconnect local devices (e.g., printers and servers) and to connect to the internet. On a wired LAN, PCs in the library are typically connected by category 5 (Cat5) cable, running the IEEE 802.3 protocol through a system of interconnected devices and eventually connect to the Internet. The cables to the servers are typically on Cat 5e enhanced cable, which will support IEEE 802.3 at 1 Gbit/s. A wireless LAN may exist using a different IEEE protocol, 802.11b, 802.11g or possibly 802.11n. The staff computers (bright green in the figure) can get to the color printer, checkout records, and the academic network and the Internet. All user computers can get to the Internet and the card catalog. Each workgroup can get to its local printer. Note that the printers are not accessible from outside their workgroup.

Typical library network, in a branching tree topology and controlled access to resources

All interconnected devices must understand the network layer (layer 3), because they are handling multiple subnets (the different colors). Those inside the library, which have only 10/100 Mbit/s Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer 3 switches" because they only have Ethernet interfaces and must understand IP. It would be more correct to call them access routers, where the router at the top is a distribution router that connects to the Internet and academic networks' customer access routers.

The defining characteristics of LANs, in contrast to WANs (wide area networks), include their higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines. Current Ethernet or other IEEE 802.3 LAN technologies operate at speeds up to 10 Gbit/s. This is the data transfer rate. IEEE has projects investigating the standardization of 40 and 100 Gbit/s.[3]

Campus area network

A campus area network (CAN) is a computer network made up of an interconnection of local area networks (LANs) within a limited geographical area. It can be considered one form of a metropolitan area network, specific to an academic setting.

In the case of a university campus-based campus area network, the network is likely to link a variety of campus buildings including; academic departments, the university library and student residence halls. A campus area network is larger than a local area network but smaller than a wide area network (WAN) (in some cases).

The main aim of a campus area network is to facilitate students accessing internet and university resources. This is a network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, office building, or a military base. A CAN may be considered a type of MAN (metropolitan area network), but is generally limited to a smaller area than a typical MAN. This term is most often used to discuss the implementation of networks for a contiguous area. This should not be confused with a Controller Area Network. A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby buildings.

Metropolitan area network

A metropolitan area network (MAN) is a network that connects two or more local area networks or campus area networks together but does not extend beyond the boundaries of the immediate town/city. Routers, switches and hubs are connected to create a metropolitan area network.

Wide area network

A wide area network (WAN) is a computer network that covers a broad area (i.e. any network whose communications links cross metropolitan, regional, or national boundaries [1]). Less formally, a WAN is a network that uses routers and public communications links Contrast with personal area networks (PANs), local area networks (LANs), campus area networks (CANs), or metropolitan area networks (MANs), which are usually limited to a room, building, campus or specific metropolitan area (e.g., a city) respectively. The largest and most well-known example of a WAN is the Internet. A WAN is a data communications network that covers a relatively broad geographic area (i.e. one city to another and one country to another country) and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer.

Global area network

A global area networks (GAN) (see also IEEE 802.20) specification is in development by several groups, and there is no common definition. In general, however, a GAN is a model for supporting mobile communications across an arbitrary number of wireless LANs, satellite coverage areas, etc. The key challenge in mobile communications is "handing off" the user communications from one local coverage area to the next. In IEEE Project 802, this involves a succession of terrestrial WIRELESS local area networks (WLAN).[4]

Virtual private network

A virtual private network (VPN) is a computer network in which some of the links between nodes are carried by open connections or virtual circuits in some larger network (e.g., the Internet) instead of by physical wires. The data link layer protocols of the virtual network are said to be tunneled through the larger network when this is the case. One common application is secure communications through the public Internet, but a VPN need not have explicit security features, such as authentication or content encryption. VPNs, for example, can be used to separate the traffic of different user communities over an underlying network with strong security features.

A VPN may have best-effort performance, or may have a defined service level agreement (SLA) between the VPN customer and the VPN service provider. Generally, a VPN has a topology more complex than point-to-point.

A VPN allows computer users to appear to be editing from an IP address location other than the one which connects the actual computer to the Internet.


An Internetwork is the connection of two or more distinct computer networks or network segments via a common routing technology. The result is called an internetwork (often shortened to internet). Two or more networks or network segments connected using devices that operate at layer 3 (the 'network' layer) of the OSI Basic Reference Model, such as a router. Any interconnection among or between public, private, commercial, industrial, or governmental networks may also be defined as an internetwork.

In modern practice, interconnected networks use the Internet Protocol. There are at least three variants of internetworks, depending on who administers and who participates in them:

  • Intranet
  • Extranet
  • Internet

Intranets and extranets may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. The Internet is not considered to be a part of the intranet or extranet, although it may serve as a portal for access to portions of an extranet.


An intranet is a set of networks, using the Internet Protocol and IP-based tools such as web browsers and file transfer applications, that is under the control of a single administrative entity. That administrative entity closes the intranet to all but specific, authorized users. Most commonly, an intranet is the internal network of an organization. A large intranet will typically have at least one web server to provide users with organizational information.


An extranet is a network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities (e.g., a company's customers may be given access to some part of its intranet creating in this way an extranet, while at the same time the customers may not be considered 'trusted' from a security standpoint). Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although, by definition, an extranet cannot consist of a single LAN; it must have at least one connection with an external network.


The Internet consists of a worldwide interconnection of governmental, academic, public, and private networks based upon the networking technologies of the Internet Protocol Suite. It is the successor of the Advanced Research Projects Agency Network (ARPANET) developed by DARPA of the U.S. Department of Defense. The Internet is also the communications backbone underlying the World Wide Web (WWW). The 'Internet' is most commonly spelled with a capital 'I' as a proper noun, for historical reasons and to distinguish it from other generic internetworks.

Participants in the Internet use a diverse array of methods of several hundred documented, and often standardized, protocols compatible with the Internet Protocol Suite and an addressing system (IP Addresses) administered by the Internet Assigned Numbers Authority and address registries. Service providers and large enterprises exchange information about the reachability of their address spaces through the Border Gateway Protocol (BGP), forming a redundant worldwide mesh of transmission paths.

Basic hardware components

All networks are made up of basic hardware building blocks to interconnect network nodes, such as Network Interface Cards (NICs), Bridges, Hubs, Switches, and Routers. In addition, some method of connecting these building blocks is required, usually in the form of galvanic cable (most commonly Category 5 cable). Less common are microwave links (as in IEEE 802.12) or optical cable ("optical fiber"). An ethernet card may also be required.

Network interface cards

A network card, network adapter, or NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer network. It provides physical access to a networking medium and often provides a low-level addressing system through the use of MAC addresses.


A repeater is an electronic device that receives a signal and retransmits it at a higher power level, or to the other side of an obstruction, so that the signal can cover longer distances without degradation. In most twisted pair Ethernet configurations, repeaters are required for cable which runs longer than 100 meters.


A network hub contains multiple ports. When a packet arrives at one port, it is copied unmodified to all ports of the hub for transmission. The destination address in the frame is not changed to a broadcast address.[5]


A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges do not promiscuously copy traffic to all ports, as hubs do, but learn which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address only to that port. Bridges do send broadcasts to all ports except the one on which the broadcast was received.

Bridges learn the association of ports and addresses by examining the source address of frames that it sees on various ports. Once a frame arrives through a port, its source address is stored and the bridge assumes that MAC address is associated with that port. The first time that a previously unknown destination address is seen, the bridge will forward the frame to all ports other than the one on which the frame arrived.

Bridges come in three basic types:

  1. Local bridges: Directly connect local area networks (LANs)
  2. Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced by routers.
  3. Wireless bridges: Can be used to join LANs or connect remote stations to LANs.


A network switch is a device that forwards and filters OSI layer 2 datagrams (chunk of data communication) between ports (connected cables) based on the MAC addresses in the packets.[6] This is distinct from a hub in that it only forwards the packets to the ports involved in the communications rather than all ports connected. Strictly speaking, a switch is not capable of routing traffic based on IP address (OSI Layer 3) which is necessary for communicating between network segments or within a large or complex LAN. Some switches are capable of routing based on IP addresses but are still called switches as a marketing term. A switch normally has numerous ports, with the intention being that most or all of the network is connected directly to the switch, or another switch that is in turn connected to a switch.[7]

Switch is a marketing term that encompasses routers and bridges, as well as devices that may distribute traffic on load or by application content (e.g., a Web URL identifier). Switches may operate at one or more OSI model layers, including physical, data link, network, or transport (i.e., end-to-end). A device that operates simultaneously at more than one of these layers is called a multilayer switch.

Overemphasizing the ill-defined term "switch" often leads to confusion when first trying to understand networking. Many experienced network designers and operators recommend starting with the logic of devices dealing with only one protocol level, not all of which are covered by OSI. Multilayer device selection is an advanced topic that may lead to selecting particular implementations, but multilayer switching is simply not a real-world design concept.


A router is a networking device that forwards packets between networks using information in protocol headers and forwarding tables to determine the best next router for each packet. Routers work at the Network Layer of the OSI model and the Internet Layer of TCP/IP.