Networking

FTP

February 19, 2011

File Transfer Protocol (FTP), a standard Internet protocol, is the simplest way to exchange files between computers on the Internet. Like the Hypertext Transfer Protocol (HTTP), which transfers displayable Web pages and related files, and the Simple Mail Transfer Protocol (SMTP), which transfers e-mail, FTP is an application protocol that uses the Internet’s TCP/IP protocols. [...]

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Cisco Router Layer by Layer Troubleshooting

February 16, 2011

Every network admin is going to have trouble with network links on a Cisco router, at one point or another. The best way to troubleshoot any networking issues is to use the OSI model and go layer by layer. In my article How to use the OSI Model to Troubleshoot Networks, we talked about the [...]

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What is a Router?

February 15, 2011

A router is a device in computer networking that forwards data packets to their destinations, based on their addresses. The work a router does it called routing, which is somewhat like switching, but a router is different from a switch. The latter is simply a device to connect machines to form a LAN. Router Working. [...]

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Routing Basics

February 11, 2011

This article introduces the underlying concepts widely used in routing protocols. Topics summarized here include routing protocol components and algorithms. In addition, the role of routing protocols is briefly contrasted with the role of routed or network protocols. What Is Routing? Routing is the act of moving information across an internetwork from a source to [...]

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High-Speed Serial Interface

February 11, 2011

The High-Speed Serial Interface (HSSI) is a DTE/DCE interface that was developed by Cisco Systems and T3plus Networking to address the need for high-speed communication over WAN links. The HSSI specification is available to any organization wanting to implement HSSI. HSSI Interface Basics HSSI defines both electrical and physical interfaces on DTE and DCE devices. [...]

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Point-to-Point Protocol

February 11, 2011

The Point-to-Point Protocol (PPP) originally emerged as an encapsulation protocol for transporting IP traffic over point-to-point links. PPP also established a standard for the assignment and management of IP addresses, asynchronous (start/stop) and bit-oriented synchronous encapsulation, network protocol multiplexing, link configuration, link quality testing, error detection, and option negotiation for such capabilities as network layer [...]

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Enhanced Interior Gateway Routing Protocol

February 11, 2011

The Enhanced Interior Gateway Routing Protocol (EIGRP) represents an evolution from its predecessor IGRP (refer to Interior Gateway Routing Protocol). This evolution resulted from changes in networking and the demands of diverse, large-scale internetworks. EIGRP integrates the capabilities of link-state protocols into distance vector protocols. Additionally, EIGRP contains several important protocols that greatly increase its [...]

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Interior Gateway Routing Protocol

February 11, 2011

The Interior Gateway Routing Protocol (IGRP) is a routing protocol that was developed in the mid-1980s by Cisco Systems, Inc. Cisco’s principal goal in creating IGRP was to provide a robust protocol for routing within an autonomous system (AS). Such protocols are known as Interior Gateway Routing Protocols. In the mid-1980s, the most popular Interior [...]

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Frame Relay

February 11, 2011

Frame Relay is a high-performance WAN protocol that operates at the physical and data link layers of the OSI reference model. Frame Relay originally was designed for use across Integrated Services Digital Network (ISDN) interfaces. Today, it is used over a variety of other network interfaces as well. This article focuses on Frame Relay’s specifications [...]

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Little about Virtual Private Networks

February 11, 2011

Virtual private networks (VPNs) are a fairly quixotic subject; there is no single defining product, nor even much of a consensus among VPN vendors as to what comprises a VPN. Consequently, everyone knows what a VPN is, but establishing a single definition can be remarkably difficult. Some definitions are sufficiently broad as to enable one [...]

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Little about Router Command Modes

February 11, 2011

Understanding Command Modes This section describes the Cisco IOS command mode structure. Each command mode supports specific Cisco IOS commands. For example, you can use the interface type number command only from global configuration mode. The following Cisco IOS command modes are hierarchical. When you begin a router session, you are in user EXEC mode. [...]

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Use of the Configuration Register on All Cisco Routers

February 11, 2011

The Purpose of the Configuration Register The configuration register can be used to change router behavior in several ways, such as: * how the router boots (into ROMmon, NetBoot) * options while booting (ignore configuration, disable boot messages) * console speed (baud rate for a terminal emulation session) The configuration register can be set from [...]

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How to Recover Cisco 3600 and 3800 Series Router Password

February 11, 2011

Introduction This document describes how to recover the enable password and the enable secret passwords. These passwords protect access to privileged EXEC and configuration modes. The enable password password can be recovered, but the enable secret password is encrypted and must be replaced with a new password. Use the procedure described in this document in [...]

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Cable Connections Between Hubs, Switches, Routers, and Workstations

February 11, 2011

Cables to Hubs, Switches, Routers, and Workstations Crossover and straight-through cables are used in order to connect switch ports or interfaces to network devices. Consult this table in order to see when to use each of these cable types. Find the device in the left-hand column and match it up with another device in the [...]

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How to configure multiple Cisco switch ports at the same time

February 11, 2011

To configure multiple switchports at the same time we use the interface range configuration command. Example: Switch(config)#interface range fastethernet0/1 – 20 Switch(config-if-range)#speed 100 Switch(config-if-range)#duplex full The previous example will hardcode the speed and duplex settings on switchports 1 to 20. But this could well have been assinging them all to the same vlan. We can [...]

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