1. Module 4 – Learning about other Devices
Testing network connections

2. Tools CDP - Ping – Packet Internet Groper
Traceroute (Trace, Tracert) –
Telnet

3. CDP Used to obtain information about neighboring Cisco devices
Uses a Layer 2 *proprietary* protocol
CDP Version 2 (CDPv2) latest version – needs IOS 12.0(3)T or later
CDP Version 1 used from IOS 10.3 to 12.0(3)T

4. CDP Protocol independent Layer 2 protocol
therefore Layer-3 independent
media independent

5. Show cdp neighbors
CDP discovers all Cisco devices that are directly connected to a local device
Show CDP Neighbors Command displays a summary of info about the neighbors

6. Show cdp neighbors CDP v1 and CDPv2 displays Device ID Local Interface
Holdtime
Capability
Platform
Port ID
CDPv2 (only) also displays
VTP management domain name
Native VLAN
Full or half-duplex

7. Show cdp entry
Show details for a specific CDP neighbors entry

8. Show cdp interface
Show CDP setup parameters for the specified interface

9. The show cdp traffic Command

10. CDP commands

11. Starting and Stopping CDP
Global cdp enable/disable
Router(config)# cdp run
Router(config)# no cdp run
Interface level cdp enable/disable
interface FastEthernet 0/0
Router(config-interface)# cdp run
Router(config-interface)# no cdp run

12. Telnet Application-level tool
Mainly used to establish remote connections to network devices

13. Telnet Operation Available in User or Privileged EXEC mode
Default inactivity time – 10 minutes
Can remotely connect to the Paris router from the Denver router
if both routers have been previously configured
Denver> telnet Paris (or connect Paris) or
Denver> telnet
Paris> ….
Paris> exit
Denver>

14. Telnet

15. Advanced Telnet Operation
Multiple Telnet sessions can be used and suspended with the Ctrl+Shift+6 then x sequence.

16. Ping Packet Internet Groper (PING) Operates at Layer 3
Uses ICMP echo request and echo response
Tests end-to-end connectivity

17. . time out PING Uses ICMP messages
Sends an ICMP echo request and waits for an ICPM echo reply
Cisco codes:
! receipt of an echo reply message
. time out
U ICMP unreachable message received (no route)
C Source Quench
ICMP unreachable message received

18. Traceroute (trace)

19. Traceroute Operates at Layer 3
Sets TTL in IP packet header to expire at subsequent routers from the closest router to the furtherest router
Tests each step along the route to destination
Cisco codes:
nn msec RTT for number of probes
* probe timed out
A administratively prohibited
Q source quench
H ICMP unreachable message received

20. Troubleshooting Ping Traceroute Telnet show interfaces show ip route
debug