CCNA 2 Week 1 Routers and WANs

Copyright © 2005 University of Bolton Welcome Back! CCNA 2 deals with routed networks You will learn how to configure and manage Cisco routers Routing protocols are explored in detail to help you design networks effectively You will learn how to use Cisco IOS

Copyright © 2005 University of Bolton Wide Area Networks Usually defined as long distance network connections (> 10 km) i.e. between cities Move network traffic through routers and switches from one LAN to another Typical WAN connection

Copyright © 2005 University of Bolton WAN Devices Routers often have WAN interfaces Modems or CSU/DSU connect to phone or higher capacity digital T1/E1 lines Communication Servers concentrate dial-up access

Copyright © 2005 University of Bolton Router Components Routers are specialized computers designed to efficiently move traffic between networks Like a PC they have CPU, Memory, System Bus and External Interfaces Memory elements include RAM, Flash, NVRAM and ROM each with specific role

Copyright © 2005 University of Bolton Router Memory ROM –Holds startup and diagnostic code Flash memory –Holds IOS Operating System NVRAM –Contains router configuration files at startup RAM –Contains current configuration files, routing tables, packet queues and network information

Copyright © 2005 University of Bolton Routers and Internetworks Routers have LAN and WAN interfaces –Can route traffic between subnets of LAN –Connect to other routers via WAN Router moves data packets from one network interface to another Routing decisions made using Layer 3 address details

Copyright © 2005 University of Bolton Routing Tables Routing decisions based on rules contained in routing tables (stored in RAM) Tables can be fixed set of rules (static) Routing table information can also be learned from neighboring routers using routing protocols (dynamic)

Copyright © 2005 University of Bolton Internetwork provides Consistent end-to-end addressing Addresses that represent network topologies Best path selection Dynamic or static routing Switching

Copyright © 2005 University of Bolton WAN Layers Which OSI layers are involved in WAN connections between routers? Physical (1) Data Link (2)

Copyright © 2005 University of Bolton DCE and DTE Connections are between: –Customer’s Data Terminal Equipment (DTE) –Supplier’s Data Circuit Equipment (DCE)

Copyright © 2005 University of Bolton CCNA Labs In real-world applications most networks rely on a telco for the WAN Here in the lab we simulate the entire WAN connection Use Cisco V.35 cables to connect pairs or routers One router acts as DCE, the other is DTE

Router Architecture

Copyright © 2005 University of Bolton CPU The Central Processing Unit (CPU) executes instructions in the operating system. Among these functions are system initialization, routing functions, and network interface control. The CPU is a microprocessor. Large routers may have multiple CPUs

Copyright © 2005 University of Bolton RAM Holds temporary information while router is running –routing table information –fast switching caches –running configurations –packet queues. The contents of RAM are lost when power is removed. RAM can be upgraded with the addition of DIMMs

Copyright © 2005 University of Bolton Flash Used for storage of a full Cisco IOS software image Can be upgraded by loading a new image into flash The IOS may be in uncompressed or compressed form Upgrades are possible using SIMMs or PCMCIA cards Flash memory

Copyright © 2005 University of Bolton NVRAM NVRAM is used to store the startup configuration Some devices use EEPROMs others use Flash In either case these devices retain contents when power is removed Cisco IOS makes a distinction between Flash and NVRAM

Copyright © 2005 University of Bolton Router Internals

Copyright © 2005 University of Bolton Router Interfaces

Copyright © 2005 University of Bolton Interface Types LAN Connections –Ethernet, Token Ring or FDDI links –Connect to local network devices directly WAN Connections –Serial or possible ISDN –Usually require connection to CSU of supplier Management Ports –Asynchronous serial connections –Text based management rather than network traffic

Copyright © 2005 University of Bolton Management Ports Used to configure router via text interface Console port features error messages and debug information Not reliant on networking protocols for access Can also manage via telnet connection remotely, but must be working first

Copyright © 2005 University of Bolton Console Port Connection Requires rollover cable Serial port on PC VT100 terminal emulator e.g. Hyperterminal

Copyright © 2005 University of Bolton LAN Ports Several RJ-45 connecters on a router – take care Cisco use a colour scheme Ethernet cable normally connects a router to a switch, with computers connected to the switch with straight-through cables Router to Router or Router to Computer connections use a cross-over cable

Copyright © 2005 University of Bolton WAN Connections Most commonly serial connections Usually have a router as Customer Premises Equipment (CPE) acting as DTE Often have DCE provided by supplier on site as DCE connected by serial cable May also connect via Modem over longer distance