Basic Router Configuration

Honolulu Community College

Cisco Academy Training Center

Semester 2

Version 2.1

Overview1. This chapter covers general information about the router.2. Elements of the Router.3. Cisco Discovery Protocol.4. Remotely accessing a router - telnet.5. Testing network connectivity: ping trace debug

Configuration Sources Router can be configured from:

console terminal (initial configuration). via modem using AUX port. virtual terminal (telnet), once configured. TFTP server on network.

Internal Configuration Components RAM/DRAM

Routing tables. ARP cache. Packet buffering Packet queues. Running configuration.

RAM contents lost when power is lost.

NVRAM - nonvolatile. Backup configuration, (startup config).

NVRAM retains data when power is turned off.

Internal Configuration Components (cont) Flash - erasable, reprogrammable ROM.

OS image & microcode. Can have multiple copies of IOS.

Flash contents are retained when power is turned off.

ROM - read only memory. POST (power on self test). Bootstrap program. Operating system software.

Internal Configuration Components Interfaces - network connections thru which

packets enter and exit the router.

Cisco Discovery Protocol (CDP) Cisco’s proprietary command. Allows access to configurations of directly

connected routers. Commands include:

cdp enable show cdp interface show cdp entry {device name} show cdp neighbors show cdp neighbors detail

Telnet Operations Telnet is a virtual terminal protocol, which

allows connections to hosts. Telnet is part of the TCP/IP protocol suite. Routers can have up to 5 simultaneous telnet

sessions. Can telnet by entering host name. EXIT or LOGOUT to end telnet session.

Telnet tests upper-layer connectivity.

Ping (ICMP)checks network connectivity (end-to-end).

Trace tests each step along the way, when data is sent.

Show ip route checks for a routing table entry.

Show interface serial displays line and data-link protocol status.

Is Link Operational? Interface has two components:

Hardware. Software.

show interface serial Command Displays line and data-link protocol status. Line status:

triggered by Carrier Detect signal.

Physical-layer status. Line protocol:

triggered by keepalive frames.

Data-link framing.

show interface Command Displays statistical data about interface. clear counters will reset counters to zero.

Debug Command Displays the specified network events on

console. Used for troubleshooting, can significantly

slow the network. undebug all command to turn debugging off. Debug messages can be diplayed on console,

telnet terminal, UNIX host, or internal buffer. terminal monitor command lets you redirect

debug data to virtual terminal (telnet).

Summary 1 Router modes in Cisco IOS.

User-mode: allows limited checks on configuration status.

Privileged-mode: allows detailed examination, remote access, debugging.

Global Configuration mode: make simple one line changes in config file.

Specific Configuration mode: make complex, multi-line changes in config file.

Setup mode: configuration dialog. RXBOOT mode: password recovery.

Summary 2 Router elements:

RAM/DRAM NVRAM Flash ROM Interfaces

CDP - to access configuration information about directly connected routers.

Summary 3 Testing:

Telnet - layer 7, can router be accessed? Ping - layer 3, are protocol packets being

routed? (end-to-end) Trace - tests each step along the way. Show ip route - looks at routing table for target

network table entry. Show interface serial - checks line and

protocol status. Debug.