CCNA :) Be a Good Network Administrator

10BASE5 7.1.2 This page will discuss the original 1980 Ethernet product, which is 10BASE5. 10BASE5 transmitted 10 Mbps over a single think coaxial cable bus. 10BASE5 is important because it was the first medium used for Ethernet. 10BASE5 was part of the original 802.3 standard. The primary benefit of 10BASE5 was length. 10BASE5 may be found in legacy installations. It is not recommended for new installations. 10BASE5 systems are inexpensive and require no configuration. Two disadvantages are that basic components like NICs are very difficult to find and it is sensitive to signal reflections on the cable. 10BASE5 systems also represent a single point of failure. 10BASE5 uses Manchester encoding. It has a solid central conductor. Each segment of thick coax may be up to 500 m (1640.4 ft) in length. The cable is large, heavy, and difficult to install. However, the distance limitations were favorable and this prolonged its use in certain applications. When the medium is a single coa...

10-Mbps Ethernet 7.1.1 This page will discuss 10-Mbps Ethernet technologies. 10BASE5, 10BASE2, and 10BASE-T Ethernet are considered Legacy Ethernet. The four common features of Legacy Ethernet are timing parameters, the frame format, transmission processes, and a basic design rule. Figure displays the parameters for 10-Mbps Ethernet operation. 10-Mbps Ethernet and slower versions are asynchronous. Each receiving station uses eight octets of timing information to synchronize its receive circuit to the incoming data. 10BASE5, 10BASE2, and 10BASE-T all share the same timing parameters. For example, 1 bit time at 10 Mbps = 100 nanoseconds (ns) = 0.1 microseconds = 1 10-millionth of a second. This means that on a 10-Mbps Ethernet network, 1 bit at the MAC sublayer requires 100 ns to transmit. For all speeds of Ethernet transmission 1000 Mbps or slower, transmission can be no slower than the slot time. Slot time is just longer than the time it theoretically can take to go from one e...

Overview Ethernet has been the most successful LAN technology mainly because of how easy it is to implement. Ethernet has also been successful because it is a flexible technology that has evolved as needs and media capabilities have changed. This module will provide details about the most important types of Ethernet. The goal is to help students understand what is common to all forms of Ethernet. Changes in Ethernet have resulted in major improvements over the 10-Mbps Ethernet of the early 1980s. The 10-Mbps Ethernet standard remained virtually unchanged until 1995 when IEEE announced a standard for a 100-Mbps Fast Ethernet. In recent years, an even more rapid growth in media speed has moved the transition from Fast Ethernet to Gigabit Ethernet. The standards for Gigabit Ethernet emerged in only three years. A faster Ethernet version called 10-Gigabit Ethernet is now widely available and faster versions will be developed. MAC addresses, CSMA/CD, and the frame format have not been...

Summary This page summarizes the topics discussed in this module. Ethernet is not one networking technology, but a family of LAN technologies that includes Legacy, Fast Ethernet, and Gigabit Ethernet. When Ethernet needs to be expanded to add a new medium or capability, the IEEE issues a new supplement to the 802.3 standard. The new supplements are given a one or two letter designation such as 802.3u. Ethernet relies on baseband signaling, which uses the entire bandwidth of the transmission medium. Ethernet operates at two layers of the OSI model, the lower half of the data link layer, known as the MAC sublayer and the physical layer. Ethernet at Layer 1 involves interfacing with media, signals, bit streams that travel on the media, components that put signals on media, and various physical topologies. Layer 1 bits need structure so OSI Layer 2 frames are used. The MAC sublayer of Layer 2 determines the type of frame appropriate for the physical media. The one thing common to all...

Link establishment and full and half duplex 6.2.10 This page will explain how links are established through Auto-Negotiation and introduce the two duplex modes. Link partners are allowed to skip offering configurations of which they are capable. This allows the network administrator to force ports to a selected speed and duplex setting, without disabling Auto-Negotiation. Auto-Negotiation is optional for most Ethernet implementations. Gigabit Ethernet requires its implementation, though the user may disable it. Auto-Negotiation was originally defined for UTP implementations of Ethernet and has been extended to work with other fiber optic implementations. When an Auto-Negotiating station first attempts to link it is supposed to enable 100BASE-TX to attempt to immediately establish a link. If 100BASE-TX signaling is present, and the station supports 100BASE-TX, it will attempt to establish a link without negotiating. If either signaling produces a link or FLP bursts are received...

Ethernet auto-negotiation 6.2.9 This page explains auto-negotiation and how it is accomplished. As Ethernet grew from 10 to 100 and 1000 Mbps, one requirement was to make each technology interoperable, even to the point that 10, 100, and 1000 interfaces could be directly connected. A process called Auto-Negotiation of speeds at half or full duplex was developed. Specifically, at the time that Fast Ethernet was introduced, the standard included a method of automatically configuring a given interface to match the speed and capabilities of the link partner. This process defines how two link partners may automatically negotiate a configuration offering the best common performance level. It has the additional advantage of only involving the lowest part of the physical layer. 10BASE-T required each station to transmit a link pulse about every 16 milliseconds, whenever the station was not engaged in transmitting a message. Auto-Negotiation adopted this signal and renamed it a Normal Li...

FCS and beyond 6.2.8 This page will focus on additional errors that occur on an Ethernet network. A received frame that has a bad Frame Check Sequence, also referred to as a checksum or CRC error, differs from the original transmission by at least one bit. In an FCS error frame the header information is probably correct, but the checksum calculated by the receiving station does not match the checksum appended to the end of the frame by the sending station. The frame is then discarded. High numbers of FCS errors from a single station usually indicates a faulty NIC and/or faulty or corrupted software drivers, or a bad cable connecting that station to the network. If FCS errors are associated with many stations, they are generally traceable to bad cabling, a faulty version of the NIC driver, a faulty hub port, or induced noise in the cable system. A message that does not end on an octet boundary is known as an alignment error. Instead of the correct number of binary bits forming ...