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Cisco Systems IntelligentGigabit Ethernet Switch Modules for the IBMBladeCenter, Software Configuration Guide
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Chapter25 Troubleshooting
Diagnosing Connectivity Problems
•A switch is reachable from another switch when you can test connec tivity by using the ping
privileged EXEC command. All switches in the physical path must be re achable 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 th e
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.
•The traceroute mac ip command output shows the Layer 2 path whe n the specified source and
destination IP addresses belong to 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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If an ARP entry exists for the specified IP address, the switch uses the associated MAC address
and identifies the physical path.
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If an ARP entry does not exist, the switch sends an ARP query and tries to resolve the IP
address. If the IP address is not resolved, the path is not identified, and an error message
appears.
•When multiple devices are attached to one port through hubs (for example, multiple CDP neighbors
are detected on a port), the Layer 2 traceroute fea ture is not supported. When more than one CDP
neighbor is detected on a port, the Layer 2 path is not identified, and an error message appear s.
•This feature is not supported in Token Ring VLANs.
Displaying the Physical Path
You can display physical path that a packet takes from a source device to a destination device by using
one of these privileged EXEC commands:
•traceroute mac [interface interface-id] {source-mac-address} [interface interface-id]
{destination-mac-address} [vlan vlan-id] [detail]
•traceroute mac ip {source-ip-address | source-hostname} {destination-ip-address |
destination-hostname} [detail]
For more information, see the command reference for this release.