Learning about Neighboring and Remote Devices

PJC CCNA Semester 2 Ver. 3.0by

William Kelly

Cisco Discovery Protocol (CDP) Basics CDP’s primary purpose is to discover all directly CDP’s primary purpose is to discover all directly

connected Cisco devicesconnected Cisco devices CDP is a layer 2 protocol linking physical layer CDP is a layer 2 protocol linking physical layer

and upper layer protocolsand upper layer protocols CDP provides info. about connected devices, CDP provides info. about connected devices,

the model number of those devices, and the the model number of those devices, and the connected interfacesconnected interfaces

CDP is a Cisco proprietary protocolCDP is a Cisco proprietary protocol CDP is media and protocol independent (can CDP is media and protocol independent (can

learn info. even if other devices use different learn info. even if other devices use different protocols)protocols)

CDP v2 is the most recent release and runs on CDP v2 is the most recent release and runs on IOS 12.0(3) and laterIOS 12.0(3) and later

Common CDP Commands

Info. from show cdp neighbors Command

Device IDDevice ID AddressAddress Port IDPort ID CapabilitiesCapabilities VersionVersion PlatformPlatform IP Network PrefixIP Network Prefix VTP Management Domain Name (CDPv2 only)VTP Management Domain Name (CDPv2 only) Native VLAN (CDP v2 only)Native VLAN (CDP v2 only) Full/Half-Duplex (CDPv2 only)Full/Half-Duplex (CDPv2 only)

Overview of Testing

Application

Presentation

Session

Transport

Network

Data Link

Physical1

2

3

4

5

6

7 Telnet

pingtrace

show ip route

show interface

Telnet and Advanced Telnet Telnet is used to verify the application layer

between the source and the destination A router can have 5 simultaneous telnet sessions

(vty 0 – 4) Telnet depends on the TCP to accurately deliver the

data Ctrl + Shift + 6 followed by hitting the letter x will

escape the current telnet session The show sessions command will display all the

current telnet sessions The resume session# will resume a particular telnet

session

Alternate Connectivity Tests ping traceroute show ip route show interfaces serial show interfaces/clear counter debug

The ping Command Ping is an echo protocol that helps evaluate

path reliability Ping is used to troubleshoot lower level OSI

connectivity The basic ping can be used in both the user

and privileged mode

Ping Return Codes

The traceroute Command Traceroute follows the route data travels

through a network and can be used to find broken network connections (broken end to end connectivity)

Traceroute can be used at the user and privileged level

Traceroute operates by sending pings with ever increasing Time to Live (TTL) values

Ctrl-Shift-6 can be used to cancel a traceroute

Traceroute Return Codes

The show ip route Command The show ip route command lists the map the

router has constructed to switch packets The output of this command is referred to as

the routing table

The show interfaces serial Command

The show interfaces serial command displays information about the serial connection between two routers The hardware including cables and interfaces The software including protocols

The states of a serial interface1. Serial0 is up, line protocol is up –

OPERATIONAL

2. Serial0 is up, line protocol is down – CONNECTION PROBLEM

3. Serial0 is down, line protocol is down – INTERFACE PROBLEM

4. Serial0 is administratively down, line protocol is down - DISABLED

Debug Commands Debug all should not be used on a

production router as it will slow down or crash your network

Use debug ? to find the appropriate debug command

Use undebug all to turn off all debugging