mtrace source src_address {destination dest_address} {group grp_address} {from from_address} {gateway gw_address} {timeout seconds} {maximum-hops number} {router-alert [include | exclude]} {vr vrname}


Traces multicast traffic from the receiver back to the source.

Syntax Description

src_address Specifies the unicast IP address of the multicast source.
dest_address Specifies the unicast IP address of the multicast group receiver.
grp_address Specifies the multicast IP address of the group.
from_address Specifies the unicast IP address of the interface where the mtrace request originates. This is used as the IP destination address of the mtrace response packet.
gw_address Specifies the gateway router IP address of the multicast router to which the unicast mtrace query is sent.
seconds Specifies a maximum time to wait for the mtrace response before making the next attempt. The range is 1–30 seconds.
number Specifies the maximum number of hops for the trace. The range is 1 to 255.
router-alert Specifies whether the router-alert option is included or excluded in mtrace packets.
vrname Specifies a VR name.


destination: IP address of interface from which mtrace query is generated.


from: IP address of interface from which mtrace query is generated.

gateway: when the destination is in the same subnet as one of the IP interfaces. For a non-local destination address, it is mandatory to provide a valid multicast router address.

timeout: 3 seconds

maximum-hops: 32

router-alert: include

vr: DefaultVR

Usage Guidelines

The multicast traceroute initiator node generates a multicast query and waits for timeout period to expire. If there is no response for the timeout period, the initiator node makes two more attempts. If no response is received after three attempts, the initiator node moves to a hop-by-hop trace by manipulating the maximum hop fields to perform a linear search.

The multicast trace response data contains the following fields:

Extreme Networks switches set the packet count statistics field to 0xffffffff to indicate that this field is not supported.

The last column of the mtrace command output displays forwarding codes, which are described in the following table.

Table 1. mtrace Command Forwarding Codes
Forwarding Code Description
Wrong interface mtrace request arrived on an interface to which this router would not forward for this source and group.
Prune sent upstream This router has sent a prune request upstream for the source and group in the mtrace request.
Output pruned This router has stopped forwarding for this source and group in response to a prune request from the next hop router.
Hit scope boundary The group is subject to administrative scoping at this hop.
No route This router has no route for the source or group and no way to determine a potential route.
Wrong Last Hop This router is not the proper last-hop router.
Not forwarding1 This router is not forwarding for this source and group on the outgoing interface for an unspecified reason.
Reached RP/Core Reached rendezvous point or core.
RPF Interface mtrace request arrived on the expected RPF interface (upstream interface) for this source and group.
Multicast disabled mtrace request arrived on an interface which is not enabled for multicast.
Info. Hidden1 One or more hops have been hidden from this trace.
No space in packet There was not enough room to insert another response data block in the packet.
Next router no mtrace1 The previous hop router does not understand mtrace requests.
Admin. Prohibiteda mtrace is administratively prohibited.


The following command initiates an mtrace for group at IP address

Switch.6 # mtrace source group
Mtrace from to Self via
-1  PIM thresh^ 0   RPF Interface
-2  PIM thresh^ 0
-3  PIM thresh^ 0
-4   PIM thresh^ 0
Round trip time 9 ms; total ttl of 4 required.


This command was first available in ExtremeXOS 12.4.

The router-alert option was added in ExtremeXOS 12.5.3.

Platform Availability

This command is available on platforms that support the appropriate license. For complete information about software licensing, including how to obtain and upgrade your license and which licenses support the IPv4 multicast feature, see the ExtremeXOS and Switch Engine 31.7 Feature License Requirements document.

1 ExtremeXOS switches along the mtrace path do not provide this forwarding code.