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How MTRACE works

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Article ID: KB16083 KB Last Updated: 23 Feb 2010Version: 1.0
Summary:
Mtrace enables (or disables) mtrace manageability on the interface. (Mtrace traces a route to the source device using a multicast address.)

set interface interface mtrace
unset interface interface mtrace
Symptoms:
Mtrace is a multicast version of traceroute, which is a software program (available natively on Windows and Unix-based machines) to determine the route through which data passes on its way to the local server.

Mtrace works similar to tracert. The tracert command executes a series of ICMP Echo requests beginning with TTL (Time To Live) set to 1 millisecond per hop and repeated three times. The TTL is then incremented by one until the route is reached. A mtrace query works in a similar way to the tracert command, but mtrace provides some additional information such as, loss rates along the links and the number of multicast packets flowing across each hop per second for that particular address. When troubleshooting, use the mtrace and tracert commands to find where multicast traffic flow stops, to verify the path of multicast traffic, and to identify sub-optimal paths. Basically, public looking glasses are useful in pinpointing a malfunctioning router because they allow you to run a traceroute on a machine other than your own.

Tip:

Windows 2000 includes the mrinfo command that displays the configuration of a multicast router. This tool is similar to mroute for Linux. You can use the configuration information to help troubleshoot multicast forwarding and routing problems. It is useful for verifying multicast neighbors, confirming that bi-directional neighbor adjacency exists, and verifying that tunnels are up in both directions.

The mrinfo command queries a specified multicast router with an Internet Group Management Protocol (IGMP) message. The response to the query contains:
           • A version number 
           • The list of interfaces and the neighbors on each interface
           • Metrics 
           • Time to Live (TTL) thresholds
           • Flags.
Solution:

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