mtrace

Function

The mtrace command enables the system to trace the multicast path or Reverse Path Forwarding (RPF) path from a multicast source to a querier or to a destination host, and output information about each hop.

Format

mtrace [ -g group | [ -gw last-hop-router | -d ] -r receiver | [ -gw last-hop-router | -b | -d ] -r receiver -g group ] [ { -mr | -ur resp-dest } | -a source-ip-address | -l [ stat-times ] [ -st stat-int ] | -m max-ttl | -q nqueries | -ts tsttl | -tr trttl | -v | -w timeout ] ^* source source-address

Parameters

Parameter	Description	Value
-g group	Specifies a multicast group address. It cannot be a reserved multicast address.	The value is in dotted decimal notation.
-gw last-hop-router	Specifies a last-hop device address when unicast packets can be transmitted between the current device and the last-hop device. After this parameter is specified, the initiating mode of MTrace is set to last-hop. IGMP query messages are sent to the last-hop device address.	The value is in dotted decimal notation.
-d	Sets the initiating mode of MTrace to destination when unicast packets can be transmitted between the current device and the destination host. IGMP query messages that carry the Router Alert option are sent to the specified destination host.	-
-r receiver	Specifies the IP address of a destination host.	The value is in dotted decimal notation.
-b	Sets the initiating mode of MTrace to all-router when you cannot determine whether the device directly connected to the destination host is the last-hop device. IGMP query messages are sent to 224.0.0.2.	-
-mr	Indicates that the response address is the traced multicast group address. This parameter applies to scenarios where the querier is in the multicast distribution tree (MDT).	-
-ur resp-dest	Specifies a unicast response address. It must be the IP address of a local interface.	The value is in dotted decimal notation.
-a source-ip-address	Specifies a source address for IGMP tracert query messages. It must be the IP address of a local interface. This parameter is not supported when the multicast path or RPF path from a multicast source to the current device is traced.	The value is in dotted decimal notation.
-l	Performs MTrace detection repeatedly and outputs traffic rate and statistics. If this parameter is not specified, MTrace detection is performed only once. If this parameter is specified, the -v configuration can be ignored.	-
stat-times	Specifies the number of times that MTrace detection is performed.	The value is an integer ranging from 2 to 65535. The default value is 65535.
-st stat-int	Specifies an interval at which hop information is output when MTrace detection is performed repeatedly.	The value is an integer ranging from 10 to 60, in seconds. The default value is 10.
-m max-ttl	Specifies the maximum number of hops for MTrace detection.	The value is an integer ranging from 1 to 255. The default value is 255.
-q nqueries	Specifies the number of retry times for MTrace detection.	The value is an integer ranging from 1 to 65535. The default value is 3.
-ts tsttl	Specifies the maximum number of hops traced in hop-by-hop mode.	The value ranges from 1 to 255. The default value is 30.
-tr trttl	Specifies a TTL value for IGMP tracert response messages sent in multicast mode.	The value is an integer ranging from 1 to 255. The default value is 30.
-v	Indicates message details, including output time and statistics.	-
-w timeout	Specifies a timeout period for IGMP tracert response messages.	The value is an integer ranging from 1 to 60, in seconds. The default value is 3.
source source-address	Specifies a multicast source address.	The value is in dotted decimal notation.

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Default Level

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Task Name and Operations

Task Name	Operations
sla	execute

Usage Guidelines

Usage Scenario

The mtrace command mainly has the following uses:

The mtrace command can be used in multicast troubleshooting and routine maintenance to locate a faulty device and reduce configuration errors.
It can be used to collect traffic statistics in path tracing and calculate the multicast traffic rate in cyclic path tracing.
The NMS analyzes faulty device information displayed in the mtrace command output and generates alarms.
The following paths can be traced:
RPF path from the multicast source to the current device
Multicast path from the multicast source to the current device
RPF path from the multicast source to the destination host
Multicast path from the multicast source to the destination host
The mtrace command has the following formats:
To trace the RPF path from the multicast source to the current device, run the mtrace source source-address command.
To trace the multicast path from the multicast source to the current device, run the mtrace -g group source source-address.
To trace the RPF path from the multicast source to the destination host, run the mtrace [ -gw last-hop-router | -d ] -r receiver source source-address command. If multiple devices are directly connected to a specified host, RPF paths initiated from different devices may be different. You can configure the -gw last-hop-router parameter to specify a last-hop device. The RPF path can thereby be determined.
To trace the multicast path from a multicast source to the destination host, run the mtrace [ -b | -gw last-hop-router | -d ] -r receiver -g group source source-address command.
To ensure that the mtrace command is run successfully, the current device must have the (S, G) entries and meet either of the following conditions:
The current device is directly connected to the destination host.
A ping test initiated from the current device to the last-hop device or destination host succeeds.
The current device is on the multicast path from the multicast source to the destination host.

Precautions

According to the standard protocol, IGMP tracert query messages sent in unicast mode to the destination and IGMP tracert response messages replied in multicast mode must carry the Router Alert option. Currently, messages of the device do not carry the Router Alert option. To ensure interconnection with devices whose messages carry the Router Alert option, specify the -gw last-hop-router parameter to set a last-hop device address and the -ur resp-dest parameter to set a unicast response address.

Specify -gw last-hop-router, -b, and -d based on the network. They help trace a path fast and accurately.

Specify -gw last-hop-router: The last-hop device address is known, and unicast packets can be sent to the last-hop device.
Specify -b: The current device is directly connected to the destination host.
Specify -d: Unicast packets can be transmitted between the current device and the destination host.
Specify none of the preceding parameters: The current device must be on the multicast path from the multicast source to the destination host. Otherwise, MTrace detection fails.

Example

# Trace the multicast path from the multicast source (10.1.0.1) to the destination host (10.1.6.4). The multicast group address is 225.0.0.1.

<HUAWEI> mtrace -b -r 10.1.6.4 -g 225.0.0.1 -tr 5 source 10.1.0.1
Press Ctrl+C to break multicast traceroute facility
 From the receiver(10.1.6.4), trace (10.1.0.1, 225.0.0.1)'s reverse path according to multicast routing-table
 Num  Reverse-Path    FwdTTL Protocol
  0   10.1.6.4
- 1   10.1.5.1        1      PIM
- 2   10.1.2.1        1      PIM
- 3   10.1.0.1        1      PIM
  In maximum-hop mode, received the response message, and multicast traceroute finished.

# Trace the RPF path from the multicast source (10.1.0.1) to the destination host (10.1.6.4). The last-hop device address is 10.1.6.3, and unicast packets can be sent to the last-hop device. Display message details.

<HUAWEI> mtrace -gw 10.1.6.3 -r 10.1.6.4 -v source 10.1.0.1
Press Ctrl+C to break multicast traceroute facility
 From the receiver(10.1.6.4), trace reverse path to source (10.1.0.1) according to RPF rules
 Num  Reverse-Path    FwdTTL Protocol
  0   10.1.6.4
- 1   10.1.5.1        1      PIM
  Incoming Interface Address: 10.1.5.1 
  Outgoing Interface Address: 10.1.6.3 
  Previous-Hop Router Address: 10.1.5.2 
  Input packet count on incoming interface: 0xffffffff 
  Output packet count on outgoing interface: 0xffffffff 
  Total number of packets for this source-group pair: 0xffffffff 
  Forwarding TTL: 1 
  Forwarding Code: NO_ERROR
- 2   10.1.2.1        1      PIM
  Incoming Interface Address: 10.1.2.1 
  Outgoing Interface Address: 10.1.5.2 
  Previous-Hop Router Address: 10.1.2.2 
  Input packet count on incoming interface: 0xffffffff 
  Output packet count on outgoing interface: 0xffffffff 
  Total number of packets for this source-group pair: 0xffffffff 
  Forwarding TTL: 1 
  Forwarding Code: NO_ERROR
- 3   10.1.0.1        1      PIM
  Incoming Interface Address: 10.1.0.1 
  Outgoing Interface Address: 10.1.2.2 
  Previous-Hop Router Address: 0.0.0.0 
  Input packet count on incoming interface: 0xffffffff 
  Output packet count on outgoing interface: 0xffffffff 
  Total number of packets for this source-group pair: 0xffffffff 
  Forwarding TTL: 1 
  Forwarding Code: NO_ERROR 
 In maximum-hop mode, received the response message, and multicast traceroute finished.

# Trace the multicast path from the multicast source (10.1.0.1) to the current device (10.1.5.1). The multicast group address is 225.0.0.1, and MTrace detection is performed twice.

<HUAWEI> mtrace -g 225.0.0.1 -l 2 -st 10 source 10.1.0.1
Press Ctrl+C to break multicast traceroute facility
 From the receiver(10.1.5.1), trace (10.1.0.1, 225.0.0.1)'s reverse path according to multicast routing-table
 In calculating-rate mode, current statistic times is: 1
- 1 10.1.5.1
   Incoming Interface Address: 10.1.5.1 Input packets rate: 0xffffffff
   Outgoing Interface Address: 0.0.0.0 Output packets rate: 0xffffffff
   Forwarding Cache (10.1.0.1, 225.0.0.1) Forwarding packets rate: 0
   The packet loss rate of (10.1.0.1, 225.0.0.1) is 0.00%
- 2 10.1.2.1
   Incoming Interface Address: 10.1.2.1 Input packets rate: 0xffffffff
   Outgoing Interface Address: 10.1.5.2 Output packets rate: 0xffffffff
   Forwarding Cache (10.1.0.1, 225.0.0.1) Forwarding packets rate: 0
   The packet loss rate of (10.1.0.1, 225.0.0.1) is 0.00%
- 3 10.1.0.1
   Incoming Interface Address: 10.1.0.1 Input packets rate: 0xffffffff
   Outgoing Interface Address: 10.1.2.2 Output packets rate: 0xffffffff
   Forwarding Cache (10.1.0.1, 225.0.0.1) Forwarding packets rate: 0
 ********************************************************
  In calculating-rate mode, reach the demanded number of statistic,and multicast traceroute finished.

# Trace the RPF path from the multicast source (10.1.0.1) to the current device (10.1.5.1).

<HUAWEI> mtrace source 10.1.0.1
Press Ctrl+C to break multicast traceroute facility
 From the receiver(10.1.5.1), trace reverse path to source (10.1.0.1) according to RPF rules
 Num  Reverse-Path    FwdTTL Protocol
  0   10.1.5.1
- 1   10.1.5.1        1      PIM
- 2   10.1.2.1        1      PIM
- 3   10.1.0.1        1      PIM
  In maximum-hop mode, received the response message, and multicast traceroute finished.

**Table 1** Description of the **mtrace** command output
Item	Description
Press Ctrl+C to break multicast traceroute facility	You can press Ctrl+C to abort the ongoing MTrace detection.
From the receiver(10.1.5.1), trace reverse path to source (10.1.0.1) according to RPF rules	RPF path from the destination host to the multicast source.
From the receiver(10.1.5.1), trace (10.1.0.1, 225.0.0.1)'s reverse path according to multicast routing-table	Multicast path from the destination host to the multicast source.
Num	Number of traced hops.
Reverse-Path	Reverse path of multicast traffic.
FwdTTL	Minimum TTL value for multicast packet forwarding.
Protocol	Multicast routing protocol used on the device.
- 1 10.1.5.1	Last hop with the address 10.1.5.1.
In maximum-hop mode, received the response message, and multicast traceroute finished.	IGMP tracert response messages are received in maximum hop tracing mode, and MTrace detection ends.
In calculating-rate mode, current statistic times is	Calculating rate mode. The current rate is calculated for the first time.
In calculating-rate mode, reach the demanded number of statistic,and multicast traceroute finished.	The required number of calculating times in calculating rate mode is reached, and MTrace detection ends.
Incoming Interface Address	IP address of a multicast inbound interface.
Outgoing Interface Address	IP address of a multicast outbound interface.
Previous-Hop Router Address	Previous-hop device address.
Input packets rate	Message receiving rate on a multicast inbound interface.
Input packet count on incoming interface	Number of messages received on a multicast inbound interface.
Output packets rate	Message sending rate on a multicast outbound interface.
Output packet count on outgoing interface	Number of messages sent on a multicast outbound interface.
Total number of packets for this source-group pair	Number of messages forwarded along a multicast path.
Forwarding Cache (10.1.0.1, 225.0.0.1) Forwarding packets rate	Rate at which a device forwards multicast packets of the (S, G) entry.
Forwarding TTL	TTL value for multicast forwarding.
Forwarding Code	Multicast forwarding code.
The packet loss rate of (10.1.0.1, 225.0.0.1) is 0.00%	Packet loss rate of multicast packets of the (S, G) entry.