1 © 2003, Cisco Systems, Inc. All rights reserved. Computer Networks 6 Layer 2 troubleshooting Halmstad University Olga Torstensson

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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