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ManualsBrandsCisco ManualsComputer equipment2970 - Catalyst Switch
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29-14
Catalyst 2970 Switch Software Configuration Guide
78-15462-03
Chapter29 Troubleshooting
Using Layer 2 Traceroute
To terminate a ping session, enter the escape sequence (Ctrl-^ X by default). You enter the default by
simultaneously pressing and releasing the Ctrl, Shift, and 6 keys, and then pressing the X key.
Using Layer 2 Traceroute
This section describes this information:
• Understanding Layer 2 Traceroute, page 29-14
• Usage Guidelines, page 29-14
• Displaying the Physical Path, page 29-15
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 determines 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 29-14. If any devices in the physical path are transparent to CDP, the switch cannot identify
the path through these devices.
Table 29-1 Ping Output Display Characters
Character Description
! Each exclamation point means receipt of a reply.
. Each period means the network server timed out while waiting for a reply.
U A destination unreachable error PDU was received.
C A congestion experienced packet was received.
I User interrupted test.
? Unknown packet type.
& Packet lifetime exceeded.