Cisco Catalyst 4500 Series Configuration Manual page 1189

Chapter 2
The traceroute mac ip command output shows the Layer 2 path when the specified source and
destination IP addresses are in the same subnet. When you specify the IP addresses, the switch uses
Address Resolution Protocol (ARP) to associate the IP addresses with the corresponding MAC addresses
and the VLAN IDs.
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Layer 2 traceroute is not supported when multiple devices are attached to one port through hubs (for
example, multiple CDP neighbors are detected on a port). When more than one CDP neighbor is detected
on a port, the Layer 2 path is not identified, and an error message appears.
This feature is not supported in Token Ring VLANs.
Examples
The following example shows how to display the Layer 2 path by specifying the source and destination
IP addresses and by using the detail keyword:
Switch# traceroute mac ip 2.2.66.66 2.2.22.22 detail
Translating IP to mac.....
2.2.66.66 =>0000.0201.0601
2.2.22.22 =>0000.0201.0201
Source 0000.0201.0601 found on con6[WS-C2950G-24-EI] (2.2.6.6)
con6 / WS-C2950G-24-EI / 2.2.6.6 :
con5 / WS-C2950G-24-EI / 2.2.5.5 :
con1 / WS-C3550-12G / 2.2.1.1 :
con2 / WS-C3550-24 / 2.2.2.2 :
Destination 0000.0201.0201 found on con2[WS-C3550-24] (2.2.2.2)
Layer 2 trace completed.
Switch#
The following example shows how to display the Layer 2 path by specifying the source and destination
hostnames:
Switch# traceroute mac ip con6 con2
Translating IP to mac .....
2.2.66.66 =>0000.0201.0601
2.2.22.22 =>0000.0201.0201
Source 0000.0201.0601 found on con6
con6 (2.2.6.6) :Fa0/1 =>Fa0/3
con5
con1
con2
Destination 0000.0201.0201 found on con2
Layer 2 trace completed
Switch#
The following example shows the Layer 2 path when Address Resolution Protocol (ARP) cannot
associate the source IP address with the corresponding MAC address:
Switch# traceroute mac ip 2.2.66.66 2.2.77.77
Arp failed for destination 2.2.77.77.
If an ARP entry exists for the specified IP address, the switch uses the associated MAC address and
identifies the physical path.
If an ARP entry does not exist, the switch sends an ARP query and tries to resolve the IP address.
The IP addresses must be in the same subnet. If the IP address is not resolved, the path is not
identified, and a message appears.
Fa0/1 [auto, auto] =>Fa0/3 [auto, auto]
Fa0/3 [auto, auto] =>Gi0/1 [auto, auto]
Gi0/1 [auto, auto] =>Gi0/2 [auto, auto]
Gi0/2 [auto, auto] =>Fa0/1 [auto, auto]
(2.2.5.5
(2.2.1.1
(2.2.2.2
Catalyst 4500 Series Switch Cisco IOS Command Reference—Release XE 3.9.xE and 15.2(5)Ex
) : Fa0/3 =>Gi0/1
) : Gi0/1 =>Gi0/2
) : Gi0/2 =>Fa0/1
traceroute mac ip
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