CCNP TSHOOT 6.0 - Cisco Learning Home

CCNPv6 TSHOOT
within them. Trunk ports are not listed.
show vlan id vlan# Displays whether the VLAN exists and, if so, which ports
are assigned to it. Includes trunk ports on which the VLAN
is allowed.
show interfaces type/# Displays interface status, IP address/prefix, load, duplex,
speed and packet statistics and errors.
show interfaces trunk Displays all trunk ports, the operational status, trunk
encapsulation, and native VLAN, as well as the list of
allowed VLANs, active VLANs, and the VLANs in Spanning
Tree Forwarding state for the trunk.
show interfaces type/#
switchport
Checks all VLAN-related parameters for a specific interface
(access ports and trunk ports).
show etherchannel summary Displays port channels, the member ports, and flags
indicating status.
Lab 4-1 Sample Troubleshooting Flows
The figure illustrates an example of a method that you could follow to diagnose and resolve Layer 2 problems.
Sample Layer 2 Troubleshooting Flow
No L3
connectivity
between
adjacent
devices
Verify through
connection testing
(ping) and ARP
cache checks
Determine
and verify L2
path
between
devices
Analyze packet
captures
Track frames
and device
MAC
addresses
along L2
path
Investigate
links where
path seems
broken
© 2009 Cisco Systems, Inc. All rights reserved. TSHOOT v1.0—15
Usually, you start troubleshooting the Layer 2 connectivity between devices because you have discovered that
there is no Layer 3 connectivity between two adjacent Layer 2 hosts, such as two hosts in the same VLAN or a
host and its default gateway. The following are typical symptoms that could lead you to start examining Layer 2
connectivity:
• Failing pings between adjacent devices. (This can also be caused by a host-based firewall that is
blocking pings.)
All contents are Copyright © 1992–2010 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information. Page 13 of 24