39-10
Cisco IE 3000 Switch Software Configuration Guide
OL-13018-03
Chapter 39 Troubleshooting
Using Layer 2 Traceroute
To end a ping session, enter the escape sequence (
Ctrl-^ X
by default). Simultaneously press and release
the
Ctrl
,
Shift
, and
6
keys and then press the
X
key.
Using Layer 2 Traceroute
These sections contain this information:
•
Understanding Layer 2 Traceroute, page 39-10
•
Usage Guidelines, page 39-10
•
Displaying the Physical Path, page 39-11
Understanding Layer 2 Traceroute
The Layer 2 traceroute feature allows the switch to identify the physical path that a packet takes from a
source device to a destination device. Layer 2 traceroute supports only unicast source and destination
MAC addresses. It finds the path by using the MAC address tables of the switches in the path. When the
switch detects a device in the path that does not support Layer 2 traceroute, the switch continues to send
Layer 2 trace queries and lets them time out.
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.
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 function properly, do not disable CDP.
For a list of switches that support Layer 2 traceroute, see the
“Usage Guidelines” section on
page 39-10
. If any devices in the physical path are transparent to CDP, the switch cannot identify
the path through these devices. For more information about enabling CDP, see
Chapter 28,
“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.
?
Unknown packet type.
&
Packet lifetime exceeded.
Table 39-1
Ping Output Display Characters (continued)
Character
Description