1. Difference Between Internet And Ethernet
2. Difference Between Fast Ethernet And Serial Interface Number

RS-232C is a long-established standard ('C' is the current version) that describes the physical interface and protocol for relatively low-speed serial data communication Networks between computers and related devices.

RS-232C is the interface that your computer uses to talk to and exchange data with your modem and other serial devices. RS-232C is the interface between your Communication networks and other communication networks.

Difference Between Fast Ethernet And Serial Interface Adapter A data packet on an Ethernet link is called an Ethernet packet, which transports an Ethernet frame as its payload. An Ethernet frame is preceded by a preamble. Because you can have an asynchronous serial interface and that would not be able to communicate to a synchronous serial interface for obvious reasons. And think of routing protocols as just plain ol' data. No different than IP, IPX, ICMP, SNA, or anything else as far as interfaces are concerned. An excellent blog by a Cisco Learning Network VIP. What is the actual difference between speed and bandwidht of a connection. For a serial interface, we can configure both bandwidht and speed. Suppose 2 routers (R1, R2) are connected with serial T1 link (1.544 Mbps). At ethernet interface (100Mbps) of R1 a Laptop (L1) is connected and on.

Somewhere in your PC, typically on a Universal Asynchronous Receiver/Transmitter (UART) chip on your motherboard, the data from your computer is transmitted to an internal or external modem (or other serial device) from its Data Terminal Equipment (DTE) interface. Since data in your computer flows along parallel circuits and serial devices can handle only one bit at a time, the UART chip converts the groups of bits in parallel to a serial stream of bits.

As your PC's DTE agent, it also communicates with the modem or other serial device, which, in accordance with the RS-232C standard, has a complementary interface called the Data Communications Equipment (DCE) interface. RTS/CTS is the way the DTE indicates that it is ready to transmit data and the way the DCW indicates that it is ready to accept data

RS232C, a standard interface approved by the Electronic Industries Alliance (EIA) for connecting serial devices. In 1987, the EIA released a new version of the standard and changed the name to EIA-232-D. And in 1991, the EIA teamed up with Telecommunications Industry association (TIA) and issued a new version of the standard called EIA/TIA-232-E. Many people, however, still refer to the standard as RS-232C, or just RS-232.

Almost all modems conform to the EIA-232 standard and most personal computers have an EIA-232 port for connecting a modem or other device. In addition to modems, many display screens, mice, and serial printers are designed to connect to a EIA-232 port. In EIA-232 parlance, the device that connects to the interface is called a Data Communications Equipment (DCE) and the device to which it connects (e.g., the computer) is called a Data Terminal Equipment (DTE).

The EIA-232 standard supports two types of connectors -- a 25-pin D-type connector (DB-25) and a 9-pin D-type connector (DB-9). The type of serial communications used by PCs requires only 9 pins so either type of connector will work equally well.

Although EIA-232 is still the most common standard for serial communication, the EIA has recently defined successors to EIA-232 called RS-422 and RS-423. The new standards are backward compatible so that RS-232 devices can connect to an RS-422 port.

RS-232 Mechanical Specification

There is a standardized pin out for RS-232 on a DB25 connector, as shown in Figure.

The essential feature ofRS-232 is that the signals are carried as single voltages referred to a common ground on pin 7. In its simplest form, the RS-232:C interface consis;9'of only two wires for data and ground. The ground is the absolute voltage reference for all the interface circuitry, the point in the circuit from which all voltages are measured. Data on pin 2 of the DTE is transmitted, while the same data on pin 2 of a DCE (modem) is received data as shown in Figure.

Data is transmitted and received on pins 2 and 3, respectively. Data Set Ready (DSR) is an indication from the Data set (the modem or DSU/CSU) that it is on. Similarly, DTR indicates that the DTE is on. Carrier Detect (CD) indicates that carrier for the transmission data is on.

Pins 4 and 5 carry the Request to Send (RTS) and Clear to Send (CTS) signals. In most situations, RTS and CTS are constantly on the communication session. However, where the DTE is connected to a multipoint line, RTS is used to turn the carrier on the modem on and off. On a multipoint line, it is imperative that only one station is transmitting at a time. When a station wants to transmit, it raises RTS. The modem turns on carrier, typically waits a few milliseconds for carrier to stabilize, and raises CTS.

The DTE transmits when it sees CTS up. When the station has finished its transmission, it drops RTS and the modem drops CTS and carrier together.

Terminals and modems usually communicate bidirectionally. Bidirectional interchange between the two devices is directly analogous to the connection of two telephones. The differences between the DTE and DCE are that DTEs transmit on pin 2 and receive on pin 3. DCEs transmit on pin 3 and receive on pin 2. When the modem is communicating with another modem, three essential links are established. These are:

1. DTE to DCE The DTE or terminal and modem or DCE talk to each other.

2. DCE to DCE The two modems on the link talk to each other. When a DCE to DCE connection is established the modem will send a connect message to the computer. The connect message specifies the computer about the baud rate being used by the two modems for communication.

In case of modems with dissimilar baud rate, the modem of higher baud rate is set to send the data at the same rate of the other modem using the computer's communication program.

3. DTE to DCE The host computer talks with its modem.

The output signal level usually swings between +12v and,-12v. RS-232 is simple, universal, well understood and supported everywhere. However, it has some serious shortcomings as an electrical interface.

First, the interface presupposes a common ground between the DTE and DCE. This is a reasonable assumption where a short cable connects a DTE and DCE in the same room, but with longer lines and connections between devices that may be on different electrical buses, this may not be true. Second, a signal on a single line is impossible to screen effectively for noise. By screening the entire cable one can reduce the influence of outside noise, but internally generated noise remains a problem. As the baud rate and line length increase, the effect of capacitance between the cables introduces serious cross talk until a point is reached where the data itself is unreadable. Low capacitance cable can reduce crosstalk. Also, as it is the higher frequencies that are the problem control of slew rate in the signal (i.e. making the signal more rounded, rather than square) also decreases the crosstalk. The original specifications for·R$-232 had no specification for maximum slew rate.

The standards for RS-232 and similar interfaces usually restrict RS-232 to 20 kbps or less and line lengths of 15m (50 ft) or less. These restrictions are mostly throwbacks to the days when 20 kbps were considered a very high line speed, and cables were thick, with high capacitance, However, in practice, RS-232 is fur more robust than the traditional specified limits of 20 kbps over u 15m line would imply. Most 56 kbps DSUs are supplied with both V.35und RS-232 ports because RS-232 is perfectly adequate at speeds up to 200 kbps. The 15 m limitation for cable length can be stretched to about 30 m for ordinary cable, if well screened and grounded, and about 100 m if the cable is Jaw capacitance as well.

This tutorial presents Cisco device naming convention and Interface Nomenclature Guide for Router and Switch. Learn the naming convention used in fixed and modular interfaces including key difference between router and switch interface nomenclature and IOS command to view interface name in detail with example.

Cisco makes a large number of products. Among those I will include 1603, 1841, 2500, 2600 series routers and 2960 series switches in this article to explain the nomenclature. As these products are the base lines for CCNA exam.

Router Interface Nomenclature

In entry level series Cisco makes two types of routers :- fixed and modular. In fixed interface series router, all slots and ports are integrated with device. In modular interface series router, we have a choice to install the ports according to requirement.

Router supports several media types of data link layer including ethernet, fastethernet, gigabitethernet, atm, bri, pri, asynch, serial and many more. In fixed interface series router, interface numbers always start with 0 (zero) and goes their way up within specific interface type.

Fixed interface series router

In fixed interface series router, the interface nomenclature is type slot_#/ port_#.

If a fixed interface router has three Ethernet and two Serial interfaces, then they would be named Ethernet 0, Ethernet 1, Ethernet 2, Serial 0 and Serial 1.

For example, 2503 series router has two fixed serial interfaces; so they would be called serial 0 and serial 1.

Let’s take one more example, 1603 Router has one Ethernet port and one BRI port; so it would be called Ethernet 0 and BRI 0.

Modular interface series router

In modular interface series router, the interface nomenclature is type slot_#/port_#.

Modular interface series router has modular slots; we can insert any supportive interface in these slots.

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For example, following 2600 series router has two slots. First slot would be slot 0; second slot would be slot 1.

If you install four serial interfaces in first slot, then they would be named 0 - 3.

This naming convention has limitation. When we insert WIC without order, configuration of one modular interface might be lost or applied to other modular interface.

For example, in above router we have two modular slots; slot 0, slot 1 and one modular interface with four serial ports. If we install this modular interface in slot 1, then the interface name would be serial 0/0, serial 0/1, serial 0/2, and serial 0/3. If you install another modular interface with two serial ports in slot 0, then new interface name would be serial 0/0, serial 0/1, serial 0/2, serial 0/3, serial 1/0 and serial 1/1. In this case old WIC interface become serial 1/0, and serial 1/1. Therefore, old interface configuration moves to new interfaces.

To overcome this limitation from Cisco 1800, Cisco 2800, and Cisco 3800 series, routers have three tired interface naming convention for WIC slots only.

New naming convention only for WIC slots is type slot_#/subslot_#/ port_#.

Ports installed directly on chassis still use classic convention that is type slot_#/ port_#.

For example in 1841 series router two Ethernet ports are installed on chassis, they have named Fast Ethernet 0/0 and Fast Ethernet 0/1.

Switch Interface Nomenclature

Entry level switches have only fixed interfaces. Higher end switches support modular slots. Modular interface series switch has same nomenclature like router.

Nomenclature of an interface on modular interface series switch is type slot_#/port_#.

In fixed interface series switch all interfaces are installed on chassis. The Catalyst 2960 series switch supports only fixed interfaces.

Nomenclature for interface on fixed interface series switch is type slot_#/port_#.

For example on 2960-8TC first Ethernet interface is called ethernet 0/1 and last Ethernet is called Ethernet 0/8.

Catalyst 2960 series switches

• For all fixed interfaces on a Cisco switch, the slot number is always 0.
• Port number on switch starts with 1 and goes their way up.

Key difference router and switch nomenclature

On router port number starts with 0( Zero). For example first Fast Ethernet port on router would be fastethernet 0/0.

On switch port number begins with 1. For example first Fast Ethernet port on switch would be fastethernet 0/1.

Cisco IOS commands to find out the name of interface

Interface naming convention may confuse you sometime, especially in exam. Use IOS inbuilt 'show ip interface brief' command to turn this confusion in surety.

On 2960 switch

Difference Between Internet And Ethernet

On 1800 series router

Difference Between Fast Ethernet And Serial Interface Number

On 2600 series router