WANs and Routers. M.Sc. Aleksandra Kanevce M.Sc. Aleksandra Bogojeska

Transcription

1 WANs and Routers M.Sc. Aleksandra Kanevce M.Sc. Aleksandra Bogojeska 1

2 Introduction to WANs A WAN is a data communications network that spans a large geographic area such as a state, province, or country. Companies use a WAN to connect various company sites so that information can be exchanged between distant offices. 2

3 WAN Characteristics Use transmission facilities provided by common carriers such as telephone companies Use serial connections Operates at the physical layer and the data link layer 3

4 WAN Types WAN communication services are usually leased from service providers Leased Line (Point-to-point) - provides a single, preestablished WAN communications path from the customer premises through a carrier network, such as a telephone company, to a remote network. Circuit-switched network - works much like a normal telephone line works for voice communication. Ex: ISDN Packet-switched network - users share common carrier resources. The carrier can then create virtual circuits between customers' sites. Ex: ATM, Frame Relay 4

5 WAN Types 5

6 Routers A router is a special type of computer. Routers connect and allow communication between two networks and determine the best path for data to travel. Routers need the Internetwork Operating System (IOS) software to run configuration files. - These configuration files contain the instructions and parameters that control the flow of traffic in and out of the routers. 6

7 What kinds of Routers are on the Internet? Router is a physical device in a network that directs packets to their intended destinations Routers are used at Three levels in the Internet Access Level Ex. Cisco 700 to 2500 Series Enterprise/Distribution Level Ex. Cisco 2600 to 3600 Series Core/Backbone Level Ex. Cisco GSR Series 7

8 Routers how they relate to LANs and WANs Routers can be used to segment LANs into different broadcast domains, but they are mainly used as WAN devices. They are the backbone devices of large intranets and of the Internet. They operate at Layer 3 of the OSI model, making decisions based on network addresses. The two main functions of a router are: -selection of best path -switching of packets to the proper interface 8

9 Types and Sizes of Routers Home Networking or Access Router 10s of $$ Router for Large Backbone Networks Routers for Small/Medium sized Enterprise Networks > 10,000s of $$ 100s-1000s of $$ 9

10 Routers Connected by WAN Technologies 10

11 IP Network View: ISPs (E.g. Internet2 - USA, DANTE - Europe, CANARIE - Canada, ) (E.g. OARnet - Ohio, MERIT - Michigan, ) (E.g. Time Warner, SBC Yahoo, WOW, ) 11

12 Point of Presence (PoP) PoP (Point of Presence) is a term used to reference a physical location where network equipment such as routers, switches, etc. are deployed. It is also where telecommunication lines meet An ISP hands-off traffic to another ISP 12

13 Router Architecture Overiew Router s Primary Functions Orchestrate routing algorithms/protocol (RIP, OSPF, BGP) Switching datagrams from incoming to outgoing link at line speed Router Interface 13

14 Router Internal Functions 14

15 Path Determination 15

16 Routing tables Routers build routing tables and exchange network information with other routers Most routing tables are maintained dynamically through the use of a routing protocol that exchanges network topology information with other routers An administrator can configure static routes to maintain routing tables 16

17 Internetwork Routers Any internetwork must include the following: Consistent end-to-end addressing Addresses that represent network topologies Best path selection Dynamic or static routing Switching 17

18 Role of routers in a WAN The main function of a router is to transmit data using Layer 3 addresses This process is also called routing When a router uses the physical and data link layer standards and protocols that are associated with WANs, it is operating as a WAN device The main role of a router in a WAN is to provide connections between the various WAN physical and data-link standards 18

19 Router Components 19

20 Router Components RAM - holds routing table info, fast switching cache, running configuration, packet queues NVRAM (non-volatile) - used to store backup/startup configuration file Flash memory - used for storage of a full Cisco IOS software image ROM used for hardware diagnostics during router bootup and loading the Cisco IOS software Interfaces router connections to the outside - console or auxiliary (AUX) - Used primarily for router initial configuration and maintenance 20

21 Router External Connections The management port provides a text-based connection for the configuration and troubleshooting of the router The common management interfaces are the console and auxiliary ports The console and auxiliary ports are connected to a communications port on a computer The computer must run a terminal emulation program to provide a text-based session with the router 21

22 External Connections on a 2600 Router 22

23 Router External Connections 23

24 Console Port Connections 1. Configure terminal emulation software on the PC for the following: The appropriate com port 9600 baud 8 data bits No parity 1 stop bit No flow control 2. Connect a rollover cable to the router console port (RJ-45 connector). 3. Connect the other end of the rollover cable to the RJ-45 to DB-9 adapter 4. Attach the female DB-9 adapter to a PC. 24

25 Computer or Terminal Console Connection 25