09-17-2010 08:09 AM - edited 03-06-2019 01:02 PM
Can someone please explain to me how the mtrace command works? Please provide an example. Thanks in advance.
09-17-2010 10:21 AM
To trace the path from a source to a destination branch for a multicast distribution tree, use the mtrace user EXEC command.
mtrace source [destination] [group]
EXEC
This command first appeared in Cisco IOS Release 11.0.
The trace request generated by the mtrace command is multicast to the multicast group to find the last hop router to the specified destination. The trace then follows the multicast path from destination to source by passing the mtrace request packet via unicast to each hop. Responses are unicast to the querying router by the first hop router to the source. This command allows you to isolate multicast routing failures.
If no arguments are entered, the router will interactively prompt you for them.
This command is identical in function to the UNIX version of mtrace.
The following is sample output from the mtrace command:
Router# mtrace 171.69.215.41 171.69.215.67 239.254.254.254
Type escape sequence to abort.
Mtrace from 171.69.215.41 to 171.69.215.67 via group 239.254.254.254
From source (?) to destination (?)
Querying full reverse path...
0 171.69.215.67
-1 171.69.215.67 PIM thresh^ 0 0 ms
-2 171.69.215.74 PIM thresh^ 0 2 ms
-3 171.69.215.57 PIM thresh^ 0 894 ms
-4 171.69.215.41 PIM thresh^ 0 893 ms
-5 171.69.215.12 PIM thresh^ 0 894 ms
-6 171.69.215.98 PIM thresh^ 0 893 ms
describes the fields shown in the display.
09-17-2010 12:28 PM
Thanks, but can you explain in simple english?
09-21-2010 03:15 AM
Do you want to know the purpose of mtrace or how it works internally ?
When I dug up a littile bit on how it works , I got this :
Mtrace use special IGMP packet type (Queries and Response) IGMP 1F and
1E. Requestor send packet to ther last-hop router. This router add some
usefull parameters such as IF, OF, input packet count, out packet count,
query time and many other. Then router send traceroute Request to the
next-hop (out to Input Interface for SPT or shared tree) and each hop add
same data to the packet. This packet extend as unicasts. At the end first-hop
router send IGMP Response to the requestor.
HTH,
Mani
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