Cisco Systems 3560 Manual Do Utilizador

Página de 1288
 
47-15
Catalyst 3560 Switch Software Configuration Guide
OL-8553-06
Chapter 47      Troubleshooting
Using Layer 2 Traceroute
To end a ping session, enter the escape sequence (Ctrl-^ X by default). Simultaneously press and release 
the CtrlShift, and 6 keys and then press the X key. 
Using Layer 2 Traceroute
These sections contain this information:
  •
  •
  •
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 
. 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 
  •
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.