CCNA 2 Week 1 Routers and WANs. Copyright © 2005 University of Bolton Welcome Back! CCNA 2 deals...

CCNA 2 Week 1

Routers and WANs

Copyright © 2005 University of BoltonCopyright © 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


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


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


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


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


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


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)


Internetwork provides

Consistent end-to-end addressing

Addresses that represent network topologies

Best path selection

Dynamic or static routing

Switching


WAN Layers

Which OSI layers are involved in WAN connections between routers?

Physical (1)

Data Link (2)


DCE and DTE

Connections are between:– Customer’s Data Terminal Equipment (DTE) – Supplier’s Data Circuit Equipment (DCE)


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


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


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


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


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


Router Internals


Router Interfaces


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


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


Console Port Connection

Requires rollover cable

Serial port on PC

VT100 terminal emulator e.g. Hyperterminal


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


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

CCNA 2 Week 1 Routers and WANs. Copyright © 2005 University of Bolton Welcome Back! CCNA 2 deals...

Documents

Transcript of CCNA 2 Week 1 Routers and WANs. Copyright © 2005 University of Bolton Welcome Back! CCNA 2 deals...