Dell S6100 Configuration Manual page 583

Scenario
If a multicast tree is not formed due to a
configuration issue (for example, PIM is not
enabled on one of the interfaces on the
path), you can invoke a weak mtrace to
identify the location in the network where the
error has originated.
If the destination provided in the command is
not a valid receiver for the multicast group,
the last hop router for the destination
provides the WRONG LAST HOP error code.
If the last-hop router contains a path to the
source, the path is traced irrespective of the
incorrect destination.
If a router in the network does not process
mtrace and drops the packet resulting in no
response, the system performs an expanding-
hop search to trace the path to the router
that has dropped mtrace. The output of the
command displays a '*' indicating that no
response is received for an mtrace request.
The following message appears when the
system performs a hop-by-hop search:
"switching to hop-by-hop:"
Output
-3 10.10.10.1
--------------------------------------------------------------
----
R1>mtrace 6.6.6.6 4.4.4.5
Type Ctrl-C to abort.
Querying reverse path for source 6.6.6.6 to destination
4.4.4.5 via RPF
From source (?) to destination (?)
--------------------------------------------------------------
---
|Hop| OIF IP
Mask|
--------------------------------------------------------------
---
0 4.4.4.5
-1 4.4.4.4
6.6.6.0/24
-2 20.20.20.2
-3 10.10.10.1
--------------------------------------------------------------
----
R1>mtrace 6.6.6.6 5.5.5.5 234.1.1.1
Type Ctrl-C to abort.
Querying reverse path for source 6.6.6.6 to destination
4.4.4.5 via group 234.1.1.1
From source (?) to destination (?)
--------------------------------------------------------------
---
|Hop| OIF IP
Mask|
--------------------------------------------------------------
---
0 5.5.5.5
-1 5.5.5.4
6.6.6.0/24
-2 20.20.20.2
-3 10.10.10.1
-4 6.6.6.6
--------------------------------------------------------------
----
R1>mtrace 99.99.99.99 1.1.1.1
Type Ctrl-C to abort.
Querying reverse path for source 99.99.99.99 to destination
1.1.1.1 via RPF
From source (?) to destination (?)
* * * * switching to hop-by-hop:
--------------------------------------------------------------
---
|Hop| OIF IP
Mask|
--------------------------------------------------------------
---
0 1.1.1.1
-1 1.1.1.1
99.99.0.0/16
-2 101.101.101.102
99.99.0.0/16
PIM No route
|Proto| Forwarding Code |Source Network/
--> Destination
PIM
PIM
PIM Multicast disabled 6.6.6.0/24
|Proto| Forwarding Code |Source Network/
--> Destination
PIM Wrong Last-Hop
PIM
PIM
--> Source
|Proto| Forwarding Code |Source Network/
--> Destination
PIM -
PIM -
default
6.6.6.0/24
6.6.6.0/24
6.6.6.0/24
Multicast Features 583