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Using mtrace Commands

You can use CLI mtrace commands to trace information about multicast paths. This section covers the following mtrace commands:

mtrace from-source—Displays information about a multicast path from a source to a receiver. See Using the mtrace from-source Command.
mtrace monitor—Monitors and displays multicast trace operations. See Using the mtrace monitor Command.

For more information about the mtrace commands, see the JUNOS Protocols, Class of Service, and System Basics Command Reference.

Using the mtrace from-source Command

To display information about a multicast path from a source to a receiver, enter the mtrace from-source command with the following syntax. Table 72 describes the mtrace from-source command options.

user@host> mtrace from-source source host <<extra-hops number> | <group address>
| <interval seconds>
| <max-hops number>
| <max-queries number>
| <response host>
| <ttl number> | <wait-time seconds>> <loop> <multicast-response | unicast-response>
<no-resolve> <no-router-alert>
<brief | detail>

Table 72: CLI mtrace from-source Command Options

Option	Description
source host	Traces the path to the specified hostname or IP address.
extra-hops number	Sets the number of extra hops to trace past nonresponsive routers. Specify a value from 0 through 255.
group address	Traces the path for the specified group address. The default value is 0.0.0.0.
interval seconds	Sets the interval between statistics gathering. The default value is 10.
max-hops number	Sets the maximum number of hops to trace toward the source. Specify a value from 0 through 255. The default value is 32.
max-queries number	Sets the maximum number of queries for any hop. Specify a value from 1 through 32. The default value is 3.
response host	Sends the response packets to the specified hostname or IP address. By default, the response packets are sent to the router that sent the requests.
ttl number	Sets the time-to-live (TTL) value in the IP header of the query packets. Specify a hop count from 0 through 255. The default value for local queries to the all routers multicast group is 1. Otherwise, the default value is 127.
wait-time seconds	Sets the time to wait for a response packet. The default value is 3 seconds.
loop	Loops indefinitely, displaying rate and loss statistics. To quit the mtrace command, press Ctrl-C.
multicast-response	Forces the responses to use multicast.
unicast-response	Forces the response packets to use unicast.
no-resolve	Does not display hostnames.
no-router-alert	Does not use the router alert IP option in the IP header.
brief	Does not display packet rates and losses.
detail	Displays packet rates and losses if a group address is specified.

Following is sample output from the mtrace from-source command:

user@host> mtrace from-source source 192.1.4.1
group 224.1.1.1

Mtrace from 192.1.4.1 to 192.1.30.2 via group 224.1.1.1
Querying full reverse path... * * 
  0  ? (192.1.30.2)
 -1  ? (192.1.30.1)  PIM  thresh^ 1  
 -2  routerC.mycompany.net (192.1.40.2)  PIM  thresh^ 1  
 -3  hostA.mycompany.net (192.1.4.1)
Round trip time 22 ms; total ttl of 2 required.

Waiting to accumulate statistics...Results after 10 seconds:

  Source        Response Dest    Overall     Packet Statistics For Traffic From
192.1.4.1  192.1.30.2       Packet      192.1.4.1 To 224.1.1.1
     v       __/  rtt   16 ms     Rate       Lost/Sent = Pct  Rate
192.168.195.37 
192.1.40.2      routerC.mycompany.net 
     v     ^      ttl    2                      0/0    = --    0 pps
192.1.40.1     
192.1.30.1      ?              
     v      \__   ttl    3                      ?/0            0 pps
192.1.30.2      192.1.30.2
  Receiver      Query Source

Each line of the trace display is usually in the following format (depending on the options selected and the responses from the routers along the path):

hop-number host (ip-address) protocolttl

Table 73 summarizes the output fields of the display.

The packet statistics gathered from Juniper Networks routers and routing nodes are always displayed as 0.

Table 73: CLI mtrace from-source Command Display Summary

Field	Description
hop-number	Number of the hop (router) along the path.
host	Hostname, if available, or IP address of the router. If the no-resolve option was entered in the command, the hostname is not displayed.
ip-address	IP address of the router.
protocol	Protocol used.
ttl	TTL threshold.
Round trip time milliseconds ms	Total time between the sending of the query packet and the receiving of the response packet.
total ttl of number required	Total number of hops required to reach the source.
Source	Source IP address of the response packet.
Response Dest	Response destination IP address.
Overall	Average packet rate for all traffic at each hop.
Packet Statistics For Traffic From	Number of packets lost, number of packets sent, percentage of packets lost, and average packet rate at each hop.
Receiver	IP address receiving the multicast packets.
Query Source	IP address of the host sending the query packets.

Using the mtrace monitor Command

To monitor and display multicast trace operations, enter the mtrace monitor command:

user@host> mtrace monitor

Mtrace query at Apr 21 16:00:54 by 192.1.30.2, resp to 224.0.1.32, qid 2a83aa
packet from 192.1.30.2 to 224.0.0.2
from 192.1.30.2 to 192.1.4.1 via group 224.1.1.1 (mxhop=60)

Mtrace query at Apr 21 16:00:57 by 192.1.30.2, resp to 224.0.1.32, qid 25dc17
packet from 192.1.30.2 to 224.0.0.2
from 192.1.30.2 to 192.1.4.1 via group 224.1.1.1 (mxhop=60)

Mtrace query at Apr 21 16:01:00 by 192.1.30.2, resp to same, qid 20e046
packet from 192.1.30.2 to 224.0.0.2
from 192.1.30.2 to 192.1.4.1 via group 224.1.1.1 (mxhop=60)

Mtrace query at Apr 21 16:01:10 by 192.1.30.2, resp to same, qid 1d25ad
packet from 192.1.30.2 to 224.0.0.2
from 192.1.30.2 to 192.1.4.1 via group 224.1.1.1 (mxhop=60)

This example displays only mtrace queries. When the Services Router captures an mtrace response, the display is similar, but the complete mtrace response is also displayed—exactly as it is displayed in mtrace from-source command output.

Table 74 summarizes the output fields of the display.

Table 74: CLI mtrace monitor Command Display Summary

Field	Description
Mtrace operation-type at time-of-day	operation-type—Type of multicast trace operation: query or response. time-of-day—Date and time the multicast trace query or response was captured.
by	IP address of the host issuing the query.
resp to address	address—Response destination address.
qid qid	qid—Query ID number.
packet from source to destination	source—IP address of the source of the query or response. destination—IP address of the destination of the query or response.
from source to destination	source—IP address of the multicast source. destination—IP address of the multicast destination.
via group address	address—Group address being traced.
mxhop=number	number—Maximum hop setting.

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