1. 1 © 2003, Cisco Systems, Inc. All rights reserved. Computer Networks 6 Layer 2 troubleshooting Halmstad University Olga Torstensson 035-167575 olga.torstensson@ide.hh.seolga.torstensson@ide.hh.se

2. 222 © 2003, Cisco Systems, Inc. All rights reserved. Module 4 Troubleshooting Layer 2 Data Link Layer Problems LAN Switching Frame Relay ISDN PPP

3. 333 © 2003, Cisco Systems, Inc. All rights reserved. Symptoms of Data Link Layer Problems

4. 444 © 2003, Cisco Systems, Inc. All rights reserved. High Layer Protocol Failure

5. 555 © 2003, Cisco Systems, Inc. All rights reserved. PING to find Boundary of Problem

6. 666 © 2003, Cisco Systems, Inc. All rights reserved. Examine Line Status

7. 777 © 2003, Cisco Systems, Inc. All rights reserved. Suboptimal Traffic Flow

8. 888 © 2003, Cisco Systems, Inc. All rights reserved. Intermittent Packet Loss

9. 999 © 2003, Cisco Systems, Inc. All rights reserved. Interface Encapsulation

10. 10 © 2003, Cisco Systems, Inc. All rights reserved. Troubleshooting LAN Switching Review theory :STP VTP

11. 11 © 2003, Cisco Systems, Inc. All rights reserved. Don’t configure VTP servers off-line – VTP advertisement revision may cause problems in the domain vtp - domain, mode, password show vlan, show vtp domain, show vtp statistics show vtp status, show vtp counters Troubleshooting VTP

12. 12 © 2003, Cisco Systems, Inc. All rights reserved. Show vtp status

13. 13 © 2003, Cisco Systems, Inc. All rights reserved. Characteristics of STP Failure & Switching Loops

14. 14 © 2003, Cisco Systems, Inc. All rights reserved. STP

15. 15 © 2003, Cisco Systems, Inc. All rights reserved. Show spanning-tree

16. 16 © 2003, Cisco Systems, Inc. All rights reserved. Troubleshooting LAN Switching  show vlan, show spanning-tree,  debug vlan packet

17. 17 © 2003, Cisco Systems, Inc. All rights reserved. Misconfigured EtherChannel