Modem vs Router

Modem vs Router

When subscribing to an ISP, they would usually provide you with a box that connects to your phone line and to your computer. This box is usually both a router and a modem. A modem is a device that negotiates the connection with your ISP through your telephone line while a router is a device that is used to connect two networks together, in this case your network to your modem.

Traditionally modems were stand alone devices that can be connected straight to your computer or to a router. It connects to the router via the standard RJ45 and with the telephone line via the smaller RJ11. Its job is simply to translate data from one protocol to another since telephone lines do not use the same signaling and transmission methods that are used in computer networks. Because of this, data isn’t being screened by the modem and any potential threat would still go through to your network.

Routers only use RJ45 since it is understood that it would only connect to computer networks. Its job is to examine a data packet and determine where it should go; it chooses the route the data should take, thus the name router. It is in a router where firewalls are implemented in order to screen out potential attacks or threats that might try to gain access to your network.

You should know that modems are the means to connect to the internet and without modems the internet would not exist. Routers on the other hand, are not really essential for internet communication. It is still possible to connect to the internet without routers just like in the old days with internal PCI modems. But you should remember that the main job of the router is to protect you from possible threats and malware, and this shouldn’t be taken very lightly.

Summary:
1. A router is used to connect two or more networks while a modem is used to connect to a phone line
2. A router only connects to RJ45 connectors while modems need an RJ45 and an RJ11 for the phone line
3. A router provides security measures to protect your network but a modem does not
4. A modem is essential to connect to the internet while a router isn’t

Read more: Difference Between Modem and Router | Difference Between | Modem vs Router http://www.differencebetween.net/object/difference-between-modem-and-router/#ixzz12KXNfZEM

Cisco Router Hardware

Hardware Components

There are 7 major internal components of a router:

• CPU
• RAM
• NVRAM
• Flash
• ROM
• Console

• Interfaces

CPU
The CPU performs functions just as it does in a normal PC. It executes commands given by the IOS using other hardware components. High-end routers may contain multiple processors or extra slots to add more CPUs later.

RAM
Random Access Memory; this component is dynamic. Meaning, its content changes constantly. The main role of the RAM is to: hold the ARP cache, Store routing tables, hold fast-switching cache, performs packet buffering, and hold queues. It also provides temporary memory for the configuration file of the router while the router is powered on. However, the RAM loses content when router is restarted or powered off. This component is upgradeable!

NVRAM
Nonvolatile RAM is used to store the startup configuration files. This type of RAM does not lose its content when the router is restarted or powered off.

Flash
Flash memory is very important because it saves your ass if you screw up the operating system configuration. It holds the Cisco IOS image file, as well as backups. This flash memory is classified as an EEPROM (Electronically Erasable Programmable Read Only Memory). The flash ROM is upgradeable in most Cisco routers.

ROM
The ROM performs the same operations as a BIOS. It holds information about the systems hardware components and runs POST when the router first starts up. This component can be upgraded by "unplugging" the chip and installing a new one. A ROM upgrade ensures newer versions of the IOS.

Console
The console consists of the physical plugs and jacks on the router. The purpose of the console is to provide access for configurations.

Interfaces
The interfaces provide connectivity to LAN, WAN, and Console/Aux. They can be RJ-45 jacks soldered onto the motherboard, transceiver modules, or card modules. Cisco routers, especially the higher-end models, can be configured in many different ways. They can use a combination of transceivers, card modules and onboard interfaces.

IP Address of a Router

Question: What Is the IP Address of a Router?

A typical home network router possesses two IP addresses, one for the internal home (LAN) and one for the external Internet (WAN) connection. How can you find the router IP addresses?

Answer:

The internal, LAN-IP address is normally set to a default, private number. Linksys routers, for example, use 192.168.1.1 for their internal IP address. D-Link and Netgear routers typically use 192.168.0.1. Some US Robotics routers use 192.168.123.254, and some SMC routers use 192.168.2.1. No matter the brand of router, its default internal IP address should be provided in documentation. Administrators often have the option to change this IP address during router setup. In any case, however, the private LAN-IP address remains fixed once set. It can be viewed from the router's administrative console.

The external, WAN-IP address of the router is set when the router connects to the Internet service provider. This address can also be viewed on the router's administrative console. Alternatively, the WAN-IP address can be found by visiting a Web-based IP address lookup service like http://checkip.dyndns.org/ from any computer on the home LAN.

Another way to identify the public IP addresses of routers, involves executing a ping or traceroute command. From inside a home network, the (DOS) command "ping -r 1" will send a message through the home router that will cause its IP address to be displayed. For example, "ping -r 1 www.yahoo.com" should result in a message like the following displayed on the command prompt:

Reply from 66.94.230.43: bytes=32 time=294ms TTL=56 Route: 209.179.21.76 ...

In this example, the IP address after "Route:" (209.179.21.76) corresponds to the router WAN address. On corporate networks, network discovery services based on SNMP can automatically determine the IP addresses of routers and many other network devices.

Cisco Router Configuration Commands

Cisco Router Configuration Commands

More Cisco information:	- Cisco Router Commands - Cisco IP Addressing Commands - Cisco IP Services Commands - Cisco Router and Switch Commands - Cisco Router Configuration Commands - LAB 1 Basic Cisco configuration commands
Other information:	- IP6 Next Generation Overview - Linux Commands- Tom's MCSE Notes - Tom's A+ Plus Notes - Tom's Networking+ (Net+) Plus Notes

Requirement	Cisco Command
Set a console password to cisco	Router(config)#line con 0 Router(config-line)#login Router(config-line)#password cisco
Set a telnet password	Router(config)#line vty 0 4 Router(config-line)#login Router(config-line)#password cisco
Stop console timing out	Router(config)#line con 0 Router(config-line)#exec-timeout 0 0
Set the enable password to cisco	Router(config)#enable password cisco
Set the enable secret password to peter. This password overrides the enable password and is encypted within the config file	Router(config)#enable secret peter
Enable an interface	Router(config-if)#no shutdown
To disable an interface	Router(config-if)#shutdown
Set the clock rate for a router with a DCE cable to 64K	Router(config-if)clock rate 64000
Set a logical bandwidth assignment of 64K to the serial interface	Router(config-if)bandwidth 64 Note that the zeroes are not missing
To add an IP address to a interface	Router(config-if)#ip addr 10.1.1.1 255.255.255.0
To enable RIP on all 172.16.x.y interfaces	Router(config)#router rip Router(config-router)#network 172.16.0.0
Disable RIP	Router(config)#no router rip
To enable IRGP with a AS of 200, to all interfaces	Router(config)#router igrp 200 Router(config-router)#network 172.16.0.0
Disable IGRP	Router(config)#no router igrp 200
Static route the remote network is 172.16.1.0, with a mask of 255.255.255.0, the next hop is 172.16.2.1, at a cost of 5 hops	Router(config)#ip route 172.16.1.0 255.255.255.0 172.16.2.1 5
Disable CDP for the whole router	Router(config)#no cdp run
Enable CDP for he whole router	Router(config)#cdp run
Disable CDP on an interface	Router(config-if)#no cdp enable

Cisco Router Show Commands

Requirement	Cisco Command
View version information	show version
View current configuration (DRAM)	show running-config
View startup configuration (NVRAM)	show startup-config
Show IOS file and flash space	show flash
Shows all logs that the router has in its memory	show log
View the interface status of interface e0	show interface e0
Overview all interfaces on the router	show ip interfaces brief
View type of serial cable on s0	show controllers 0 (note the space between the 's' and the '0')
Display a summary of connected cdp devices	show cdp neighbor
Display detailed information on all devices	show cdp entry *
Display current routing protocols	show ip protocols
Display IP routing table	show ip route
Display access lists, this includes the number of displayed matches	show access-lists
Check the router can see the ISDN switch	show isdn status
Check a Frame Relay PVC connections	show frame-relay pvc
show lmi traffic stats	show frame-relay lmi
Display the frame inverse ARP table	show frame-relay map

Cisco Router Basic Operations

Requirement	Cisco Command
Enable	Enter privileged mode
Return to user mode from privileged	disable
Exit Router	Logout or exit or quit
Recall last command	up arrow or <Ctrl-P>
Recall next command	down arrow or <Ctrl-N>
Suspend or abort	<Shift> and  <Ctrl> and 6 then x
Refresh screen output	<Ctrl-R>
Compleat Command	TAB

Cisco Router Copy Commands

Requirement	Cisco Command
Save the current configuration from DRAM to NVRAM	copy running-config startup-config
Merge NVRAM configuration to DRAM	copy startup-config running-config
Copy DRAM configuration to a TFTP server	copy runing-config tftp
Merge TFTP configuration with current router configuration held in DRAM	copy tftp runing-config
Backup the IOS onto a TFTP server	copy flash tftp
Upgrade the router IOS from a TFTP server	copy tftp flash

Cisco Router Debug Commands

Requirement	Cisco Command
Enable debug for RIP	debug ip rip
Enable summary IGRP debug information	debug ip igrp events
Enable detailed IGRP debug information	debug ip igrp transactions
Debug IPX RIP	debug ipx routing activity
Debug IPX SAP	debug IPX SAP
Enable debug for CHAP or PAP	debug ppp authentication
Switch all debugging off	no debug all undebug all

Disclaimer:

What is the difference between a router and hub or switch?

Answer: A router is a more sophisticated network device than either a switch or a hub. Like hubs and switches, network routers are typically small, box-like pieces of equipment that multiple computers can connect to. Each features a number of "ports" the front or back that provide the connection points for these computers, a connection for electric power, and a number of LED lights to display device status. While routers, hubs and switches all share similiar physical appearance, routers differ substantially in their inner workings.

Traditional routers are designed to join multiple area networks (LANs and WANs). On the Internet or on a large corporate network, for example, routers serve as intermediate destinations for network traffic. These routers receive TCP/IP packets, look inside each packet to identify the source and target IP addresses, then forward these packets as needed to ensure the data reaches its final destination.

Routers for home networks (often called broadband routers) also can join multiple networks. These routers are designed specifically to join the home (LAN) to the Internet (WAN) for the purpose of Internet connection sharing. In contrast, neither hubs nor switches are capable of joining multiple networks or sharing an Internet connection. A home network with only hubs and switches must designate one computer as the gateway to the Internet, and that device must possess two network adapters for sharing, one for the home LAN and one for the Internet WAN. With a router, all home computers connect to the router equally, and it performs the equivalent gateway functions.

Additionally, broadband routers contain several features beyond those of traditional routers. Broadband routers provide DHCP server and proxy support, for example. Most of these routers also offer integrated firewalls. Finally, wired Ethernet broadband routers typically incorporate a built-in Ethernet switch. These routers allow several hubs or switches to be connected to them, as a means to expand the local network to accomodate more Ethernet devices.

In home networking, hubs and switches technically exist only for wired networks. Wi-Fi wireless routers incorporate a built-in access point that is roughly equivalent to a wired switch.

Type 2 Routers.

Routing EDA - Types of Routers

The task of all routers is the same. They are given some pre-existing polygons consisting of pins (also called terminals) on cells, and (optionally) some pre-existing wiring called preroutes. Each of these polygons is associated with a net, usually by name or number. The primary task of the router is to create geometries such that all terminals assigned to the same net are connected, no terminals assigned to different nets are connected, and all design rules are obeyed. A router can fail by not connecting terminals that should be connected (an open), by mistakenly connecting two terminals that should not be connected (a short), or by creating a design rule violation. In addition to correctly connecting the nets, routers may also be expected to make sure the design meets timing, has no crosstalk problems, meets any metal density requirements, and so on. This long list of often conflicting objectives is what makes routing difficult.
The four main types of routers are:

• Maze routers.
• Line probe routers
• Channel routers
• Area routers

Types of Routers?

<u>Router - Types of routers</u>

In the original era of routing (from the mid-1970s through the 1980s), general-purpose mini-computers served as routers. Although general-purpose computers can perform routing, modern high-speed routers are highly specialised computers, generally with extra hardware added to accelerate both common routing functions such as packet forwarding and specialised functions such as IPsec encryption.

Other changes also improve reliability, such as using DC power rather than line power (which can be provided from batteries in data centers), and using solid-state rather than magnetic storage for program loading. Large modern routers have thus come to resemble telephone switches, with whose technology they are currently converging and may eventually replace, whilst small routers have become a common household item.

A router that connects clients to the Internet is called an edge router. A router that serves solely to transmit data between other routers, e.g. inside the network of an Internet service provider, is called a core router.

A router is normally used to connect at least two networks, but a special variety of router is the one-armed router, used to route packets in a virtual LAN environment. In the case of a one-armed router the multiple attachments to different networks are all over the same physical link.

In mobile ad-hoc networks every host performs routing and forwarding by itself, while in wired networks there is usually just one router for a whole broadcast domain.

In recent times many routing functions have been added to LAN switches (a marketing term for high-speed bridges), creating "Layer 2/3 Switches" which route traffic at near wire speed.

Routers are also now being implemented as Internet gateways, primarily for small networks like those used in homes and small offices. This application is mainly where the Internet connection is an always-on broadband connection like cable modem or DSL. These are routers in the true sense because they join two networks together - the WAN and the LAN – and have a routing table. Often these small routers support the RIP protocol, although in a home application the routing function does not serve much purpose since there are only two ways to go - the WAN and the LAN. In addition, these routers typically provide DHCP, NAT, DMZ and Firewall services. Sometimes these routers can provide content filtering and VPN. Typically they are used in conjunction with either a cable modem or DSL modem, but that function can also be built-in.

Wireless Router

A wireless router is a device that performs the functions of a router but also includes the functions of a wireless access point. It is commonly used to allow access to the Internet or a computer network without the need for a cabled connection. It can function in a wired LAN (local area network), a wireless only LAN, or a mixed wired/wireless network. Most current wireless routers have the following characteristics:

• LAN ports, which function in the same manner as the ports of a network switch
• A WAN port, to connect to a wide area network, typically one with Internet access. External destinations are accessed using this port. If it is not used, many functions of the router will be bypassed.
• Wireless antennae. These allow connections from other wireless devices (NICs (network interface cards), wireless repeaters, wireless access points, and wireless bridges, for example), usually using the Wi-Fi standard.

[edit] Major manufacturers

How router works?

A router is a networking element that controls Internet and LAN traffic, shares the available bandwidth between multiple connected computers, filters packets, acts as a hardware firewall based on its configuration, network gateway, NAT server and wireless Access Point .A wireless router is essentially a bunch of network cards connected internally by an intelligent switch that directs the incoming/outgoing traffic between them.

A hardware router functions by comparing IP addresses with written rules and directs traffic packages to destination IP addresses. All Internet connections we initiate between two points are passing through multiple routers on their way to reach final point, and all routers are filtering the packages according to established rules and then pointing packet in the right direction. If a package does not meet criteria it can be deleted, therefore never reaching its destination.

A network router adds a new layer of security, better than most software security solutions you have installed on your system. It's also faster at filtering traffic and requires less resource than a software level of security to do its job. Most routers can be firmware upgraded to add new functions and encryption protocols, repair bugs, but this depends on the manufacturer, it's not a rule.

Ethernet (Local Area Network) network packets can't usually pass through a router, and that implies you can't share files and folders between computers located on both sides of a router, but there are a few workarounds like VPN tunnels, remote desktop connection software, or routers configured as a bridge between two networks.

Wireless routers have gained popularity in the recent years as they allow one to connect to any network remotely from anywhere. Moreover, you need not worry about the messy cables and wires which are connected to wired networks. The installation of wired networks can be a costly and time consuming process, for which you would need to make holes in the walls for the connection to be transferred from one room or floor to another room or floor. Wireless routers prevent all such issues. They are nowadays installed at airports, malls, large departmental stores, railway stations etc. They are many companies that manufacture wireless routers which are becoming more reliable due to the benefits they provide.

Wireless routers are considered to be the heart of wireless networks. They function in the same way as a cordless phone base station. A wireless router is a hardware device which carries out the functions of an access point as well as the router itself. The main aim of the access point is to connect computers in the facility to one another and then connect them all to the Internet. It helps in sharing a single Internet connection with many computers without a need to pay extra as Internet subscription fees for each individual user. The normal range of the wireless signal is 100 feet within which the users can use the Internet.

Read more: http://www.articlesbase.com/hardware-articles/what-is-router-and-how-it-works-1310934.html#ixzz12KRNwwwn
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What is Router?

<content></p>A router is an electronic device that interconnects two or more computer networks, and selectively interchanges packets of data between them. Each data packet contains address information that a router can use to determine if the source and destination are on the same network, or if the data packet must be transferred from one network to another. When multiple routers are used in a large collection of interconnected networks, the routers exchange information about target system addresses, so that each router can build up a table showing the preferred paths between any two systems on the interconnected networks.

A router is a networking device whose software and hardware are customized to the tasks of routing and forwarding information. A router has two or more network interfaces, which may be to different physical types of network (such as copper cables, fiber, or wireless) or different network standards. Each network interface is a specialized device that converts electric signals from one form to another.

Routers connect two or more logical subnets, each having a different network address. The subnets in the router do not necessarily map one-to-one to the physical interfaces of the router.^[1] The term "layer 3 switching" is often used interchangeably with the term "routing". The term switching is generally used to refer to data forwarding between two network devices with the same network address. This is also called layer 2 switching or LAN switching.

Conceptually, a router operates in two operational planes (or sub-systems):^[2]

• Control plane: where a router builds a table (called routing table) as how a packet should be forwarded through which interface, by using either statically configured statements (called static routes) or by exchanging information with other routers in the network through a dynamical routing protocol;
• Forwarding plane: where the router actually forwards traffic (called packets in IP) from ingress (incoming) interfaces to an egress (outgoing) interface that is appropriate for the destination address that the packet carries with it, by following rules derived from the routing table that has been built in the control plane.