1. Module 9
Troubleshooting

2. Troubleshooting using routing tables
Network testing and troubleshooting can be consuming
Efficient testing and troubleshooting must be done in a

3. show ip route show ip route command
contains entries for all known networks and subnetworks,

4. Gateway of last resort AKA Syntax used when the router is
ip default-network network
establishes a default route in networks using dynamic routing protocols or
ip route [next-hop-ip-address | exit-interface]

5. Movement of a pdu from source to destination
Both Layer 2 and Layer 3 addresses are used to get packet from source to destination
Layer 3 address is used to route the packet from the ________________ _______________________________
L3 addresses never change
Layer 2 address is used for __________ _____________________________
L2 addresses change at each hop

6. Administrative Distance
administrative distance is a
metric is considered only after the field has been narrowed by

7. Troubleshooting tips
Maintain an orderly process and structure when figuring out the problem
ping command is used at _________ to test connectivity.
telnet command may be used to verify ___________________________________________________________________
Also used for verification of the application layer software between source and destination

8. Interpreting “show interfaces”
command displays the status and global parameters associated with all interfaces
status of two important portions of the interfaces is shown
related to the
includes cables, connectors and shows the condition of the physical connection between the devices
related to
shows the state of messages such as ___________ ____________________________________________________________________________________

9. Show interface cont…
Keepalives are defined as messages sent by one network device to inform another network device that the virtual circuit between the two is still active

10. Other stats provided by “Show int”
Increasing number of carrier transitions counts on a serial link may indicate one or more of the following problems:
Line interruptions due to problems in the service provider network.
Faulty switch, CSU/DSU, or router hardware
Increasing number of input errors could mean:
Faulty telephone company equipment
Noisy serial line
Incorrect cable or cable length
Damaged cable or connection
Defective CSU or DSU
Defective router hardware

11. show ip protocol
Command displays values about _____ _______________________________________________________
used to confirm ________________________________
which _________ _______________
which interfaces are sending updates
______________ _______________

12. show ip protocol cont…
also shows timers, filters, route summarization, route redistribution, and other parameters
can be used to diagnose a multitude of routing issues
Check out all of these when doing labs…

13. Labs for MOD 9 Troubleshooting Using Ping and Telnet
Using show ip route to examine routing tables
Troubleshooting routing issues with show ip route and show ip protocols
Troubleshooting routing issues with debug
Troubleshooting using Trace Route