tracert lsp (General)

Function

The tracert lsp command enables the system to trace the gateways along the LSP from the source to the destination.

Format

tracert lsp [ -a source-ip | -exp exp-value | -h ttl-value | -r reply-mode | -t time-out | -s packet-size | -g ] ^* te { tunnelName | ifType ifNum } [ hot-standby | primary ] [ compatible-mode ] [ detail ]

tracert lsp [ -a source-ip | -exp exp-value | -h ttl-value | -t time-out | -s packet-size | -g | -r reply-mode ] ^* segment-routing { { auto-tunnel srAutoTunnelName [ version { draft2 | draft4 | rfc8287 } ] } | te { tunnelName | ifType ifNum } [ draft2 | rfc8287 ] } [ hot-standby | primary ] [ detail ]

tracert lsp [ -a source-ip | -exp exp-value | -h ttl-value | -t time-out | -g ] ^* te { auto-tunnel auto-tunnelname } [ detail ]

tracert lsp [ -a source-ip | -exp exp-value | -h ttl-value | -s packet-size | -t time-out | -g ] ^* general labels [ mplsLabel1 [ mplsLabel2 [ mplsLabel3 [ mplsLabel4 [ mplsLabel5 [ mplsLabel6 [ mplsLabel7 [ mplsLabel8 [ mplsLabel9 [ mplsLabel10 [ mplsLabel11 [ mplsLabel12 [ mplsLabel13 ] ] ] ] ] ] ] ] ] ] ] ] ] -i { outIfName | outIfType outIfNum } nexthop nexthopAddr

Parameters

Parameter	Description	Value
-a source-ip	Specifies the source address of MPLS Echo Request packets to be sent. If no source address is specified, the MPLS LSR ID is used as the source address of the MPLS Echo Request packet.	The value is in dotted decimal notation.
-exp exp-value	Specifies the number of MPLS Echo Request packets to be sent. When the network quality is poor, you can increase the number of sent packets to detect the network quality based on the packet loss rate.	The value is an integer ranging from 1 to 4294967295.
-h ttl-value	Specifies the TTL value. If the TTL value in a packet is reduced to 0 during forwarding, the router that the packet reaches sends an ICMP timeout packet to the source, indicating that the destination is unreachable.	The value is an integer that ranges from 1 to 255.
-r reply-mode	Specifies the mode in which the peer returns MPLS Echo Reply packets.	The value is a decimal integer ranging from 1 to 4. The default value is 2. 1: no reply. 2: The peer end responds with IPv4/IPv6 UDP packets. 3: The peer end responds with an IPv4 or IPv6 UDP packet carrying the Router Alert option. 4: reply through the control channel of the application plane.
-t time-out	Specifies the timeout period for waiting for an MPLS Echo Reply packet after an MPLS Echo Request packet is sent.	The value is an integer ranging from 0 to 65535, in milliseconds.
-s packet-size	Indicates the length of the sent payload packet, that is, the length of the packet excluding the IP header and UDP header.	The value is an integer that ranges from 84 to 9600, in bytes.
-g	Indicates MPLS packet fragmentation.	-
ip destination-iphost	Specifies the IPv4 address or host name of the peer.	If the value is an IP address, it is in dotted decimal notation. If the value is a hostname, it is a string of 1 to 255 case-sensitive characters, spaces not supported.
mask-length	Specifies the mask length of the destination address.	The value is an integer ranging from 0 to 32.
ip-address	Specifies the destination address in the IP header of an MPLS tracert packet with the prefix being 127.0.0.0/8. The destination address in the IP header can be changed to trace a test packet.	By default, the destination IP address in the IP header of an MPLS tracert packet is 127.0.0.1.
nexthop nexthopAddr	Specifies an IP address for the next hop. This parameter is used when the ingress node has one or more next hops. You can specify this parameter to select one tunnel for connectivity check.	The value is in dotted decimal notation.
detail	Displays detailed information.	-
ddmap	Specifies the packet fragmentation flag.	-
te tunnelName	Specifies the name of a TE tunnel interface.	The value is a string of 1 to 63 case-sensitive characters, spaces not supported.
ifType	Specifies an interface type.	-
ifNum	Specifies the number of an interface.	The value is a string of 1 to 63 case-sensitive characters, spaces not supported.
hot-standby	Indicates that the bypass LSP of the tunnel is detected.	-
primary	Indicates that the primary LSP of a tunnel is monitored.	-
compatible-mode	Specifies the interworking compatibility mode.	-
segment-routing	Segment routing.	-
auto-tunnel auto-tunnelname	Specifies the name of a dynamic tunnel interface.	The value is a string of 1 to 31 case-sensitive characters. It cannot contain spaces.
srAutoTunnelName	Specifies the name of an automatically generated TE tunnel interface.	The value is a string of 1 to 255 case-sensitive characters. It cannot contain spaces.
version	Specifies the command application version.	-
draft2	Indicates that the command application version is draft2. In the SR MPLS scenario, to check LSP connectivity in compliance with the Draft-ietf-mpls-spring-lsp-ping-02 protocol draft, specify this parameter.	-
draft4	Indicates that the command application version is draft4. In the SR MPLS scenario, to check LSP connectivity in compliance with the Draft-kumarkini-mpls-spring-lsp-ping-04 protocol draft, specify this parameter.	-
rfc8287	Indicates that the RFC8287 protocol is used.	-
general	Indicates general ping detection.	-
labels mplsLabel1	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
mplsLabel2	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
mplsLabel3	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
mplsLabel4	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
mplsLabel5	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
mplsLabel6	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
mplsLabel7	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
mplsLabel8	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
mplsLabel9	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
mplsLabel10	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
mplsLabel11	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
mplsLabel12	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
mplsLabel13	Specifies an MPLS label.	The value is an integer that ranges from 0 to 1048575.
-i outIfName	Specifies an interface name.	The value is a string of 1 to 63 case-sensitive characters. It cannot contain spaces.
outIfType	Specifies an interface type.	-
outIfNum	Specifies the number of an interface.	The value is a string of 1 to 63 case-insensitive characters. It cannot contain spaces.
multi-loopback-address	Specifies the multi-path loopback address to be checked.	-
begin-address	Specifies the start destination address in the IP header of an MPLS tracert packet.	The value ranges from 127.0.0.0 to 127.255.255.255, in dotted decimal notation. The default value is 127.0.0.0.
to end-address	Specifies the end destination address in the IP header of an MPLS tracert packet.	The value ranges from 127.0.0.0 to 127.255.255.255, in dotted decimal notation. The default value is 127.0.0.31.

Views

All views

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
tailmode1	execute

Usage Guidelines

Usage Scenario

The ping lsp command can be used to check the connectivity of LSPs on an MPLS network, and the tracert lsp command can be used to locate the faulty node.

LSP tracert uses MPLS Echo Request and MPLS Echo Reply messages to detect LSP faults. Both Echo Request and Echo Reply packets are transmitted in the format of UDP packets with the port number being 3503. The receive end uses the UDP port number to identify MPLS Echo Request and Reply messages. An MPLS Echo Request packet carries FEC information to be detected, and is sent along the same LSP as other packets with the same FEC information. In this manner, the connectivity of the LSP is checked. MPLS Echo Request packets are forwarded to the destination using MPLS, whereas MPLS Echo Reply packets are forwarded to the source using IP.

For the types of links that can be detected by LSP tracert, see Configuration > System Monitoring > Ping and Tracert Configuration > Using Ping/Tracert to Check an MPLS Network > Using Tracert to Check Path Information on an MPLS Network.

Prerequisites

Before initiating a trace test, ensure that the UDP module of each node works properly.
Ensure that the MPLS module of each node is enabled and works properly.
Ensure that the ICMP module of each node works properly. Otherwise, a message is returned, indicating the trace test times out.

Implementation Procedure

The execution process of the tracert lsp command is as follows:

The source sends an MPLS Echo Request packet with the TTL being 1. After the TTL times out, the first hop sends an MPLS Echo Response packet to the source.
The source sends an MPLS Echo Request packet with the TTL being 2. After the TTL times out, the second hop sends an MPLS Echo Response packet to the source.
The source sends an MPLS Echo Request packet with the TTL being 3. After the TTL times out, the third hop sends an MPLS Echo Response packet to the source.
The preceding process repeats until the packet reaches the destination.
After receiving the MPLS Echo Request packet, the destination device of each hop replies with an MPLS Echo Response packet, indicating that the tracert lsp command is executed. In the command output of the source device, you can view the path that the packet passes through.

Configuration Impact

To prevent the egress node from forwarding the received MPLS Echo Request message to other nodes, set the destination address in the IP header of the message to a loopback address with the prefix being 127.0.0.0/8.

Precautions

If LDP is not enabled on the transit node, the transit node returns an unreachable packet when the tracert lsp te Tunnel interface-number command is run to detect the tunnel.

Example

# Trace the LSP to 4.4.4.9/32.

<HUAWEI> tracert lsp ip 4.4.4.9 32
  LSP Trace Route FEC: LDP IPV4 PREFIX 4.4.4.9/32 , press CTRL_C to break.
  TTL   Replier            Time    Type      Downstream
  0                                Ingress   10.1.2.2/[1028 ]
  1     10.1.2.2           94 ms   Transit   10.1.5.2/[3 ]
  2     10.1.5.2           94 ms   Egress

**Table 1** Description of the **tracert lsp (General)** command output
Item	Description
press CTRL_C to break	You can press CTRL+C to stop the ongoing tracert test.
TTL	Number of gateways through which the packet passes.
Replier	IP address of the transit node sending an MPLS Echo Response packet.
Time	Round-Trip Time (RTT) value, in milliseconds.
Type	Type of a node. The value can be: Ingress node. Transit node. Egress node.
Downstream	Next-hop address and pushed label value.