Specifications

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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 29 Troubleshooting
Diagnosing Connectivity Problems
The switch can only identify the path from the source device to the destination device. It cannot identify
the path that a packet takes from source host to the source device or from the destination device to the
destination host.
Switches Supporting Layer 2 Traceroute
The Layer 2 traceroute feature is available on these switches:
• Catalyst 2950 and Catalyst 2955 switches running Release 12.1(12c)EA1 or later
• Catalyst 3550 switches running Release 12.1(12c)EA1 or later
• Catalyst 4000 switches running Catalyst software Release 6.2 or later for the supervisor engine
• Catalyst 5000 switches running Catalyst software Release 6.1 or later for the supervisor engine
• Catalyst 6000 switches running Catalyst software Release 6.1 or later for the supervisor engine
Usage Guidelines
These are the Layer 2 traceroute usage guidelines:
• Cisco Discovery Protocol (CDP) must be enabled on all the devices in the network. For Layer 2
traceroute to functional properly, do not disable CDP.
For a list of switches that support Layer 2 traceroute, see the “Switches Supporting Layer 2
Traceroute” section on page 29-13. If any devices in the physical path are transparent to CDP, the
switch cannot identify the path through these devices.
Note For more information about enabling CDP, see Chapter 21, “Configuring CDP.”
• A switch is reachable from another switch when you can test connectivity by using the ping
privileged EXEC command. All switches in the physical path must be reachable from each other.
• The maximum number of hops identified in the path is ten.
• You can enter the traceroute mac or the traceroute mac ip privileged EXEC command on a switch
that is not in the physical path from the source device to the destination device. All switches in the
path must be reachable from this switch.
• The traceroute mac command output shows the Layer 2 path only when the specified source and
destination MAC addresses belong to the same VLAN. If you specify source and destination MAC
addresses that belong to different VLANs, the Layer 2 path is not identified, and an error message
appears.
• If you specify a multicast source or destination MAC address, the path is not identified, and an error
message appears.
• If the source or destination MAC address belongs to multiple VLANs, you must specify the VLAN
to which both the source and destination MAC addresses belong. If the VLAN is not specified, the
path is not identified, and an error message appears.