Layer 2

When troubleshooting Layer 2 issues, verify:

That the MAC addresses are learned, in the correct VLAN, and are not blackhole entries.
1. To display FDB entries, use the show fdb command.
Your VLAN configuration, including the VLAN tag, ports in the VLAN, and whether or not the ports are tagged.
1. To display detailed information for each VLAN configured on the switch, use the show vlan detail command.
  For additional VLAN troubleshooting tips, see VLANs.
Your STP configuration, including the STP domain (STPD) number, VLAN assignment, and port state.
1. To display STP information, use the following commands:
  show stpd detail—Displays the STP settings on the switch
  
  show stpd ports—Displays the STP state of a port
  
  show vlan stpd—Displays the STP configuration of the ports assigned to a specific VLAN
  
  For additional STP troubleshooting tips, see STP.