Troubleshooting

  1. Troubleshooting
    • Always use a systematic and methodical approach to troubleshooting.The first command to issue is:
    • Router#show ip interface brief

    This is to check if the interfaces are down or up. There are only a handful of ways to break any network in the exam.
  2. Layer 1
    Ensure that there is a clock rate on the DCE interface

    • Use command:
    • Router#show controllers serial X

    to check what type of cable is attached – where X is the serial interface number.

    Ensure that the "no shut" command has been applied to the interface.
  3. Layer 2
    Ensure that the correct encapsulation type is on the interface i.e. HDLC, PPP etc

    • Use command:
    • Router#show interface serial X

    If it is not then go into interface configuration mode and change it.
  4. Layer 3
    Ensure that the correct IP address AND subnet mask is applied to the interface.

    Ensure that the correct networks are being advertised by the routing protocol

    • Use command:
    • Router#show ip protocols

    Always ensure that you can ping across directly connected router interfaces BEFORE applying routing protocols and access lists.
Author
kraqus
ID
259818
Card Set
Troubleshooting
Description
Cisco CCNA Exam
Updated