tracert lsp (All views)

Function

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

Format

tracert lsp [ -a source-ip | -exp exp-value | -h ttl-value | -t time-out | -s size | -g ] ^* segment-routing ip ip-address mask-length [ flex-algo flex-algo-id ] [ version draft2 ] [ bypass ] [ remote remote-ip ]

tracert lsp [ -a source-ip | -exp exp-value | -h ttl-value | -t time-out | -s size | -g ] ^* sr-te policy { policy-name policyname | endpoint-ip endpoint-ip color colorid | binding-sid bsid }

Parameters

Parameter	Description	Value
-a source-ip	Specifies a source IP address of the MPLS Echo Request packet to be sent. If no source IP address is specified, the IP address of the outbound interface is used as the source IP address of Echo Request messages to be sent.	The value is in dotted decimal notation.
-exp exp-value	Specifies the EXP value of an Echo Request packet to be sent.	The value is an integer that ranges from 0 to 7. The default value is 0.
-h ttl-value	Specifies the TTL value of MPLS Echo Request packets to be sent. The TTL field in the IP packet header specifies the lifetime of the packet and specifies the maximum number of routers that the packet can pass through. The TTL field is set by the source host that sends the packet. The value of the TTL field decreases by 1 each time the packet passes through a router. When the value of the TTL field is 0, the packet is discarded and a timeout packet is sent to notify the source host.	The value is an integer ranging from 1 to 255. The default value is 30.
-t time-out	Specifies the period of time for waiting for an MPLS Echo Reply packet.	The value is an integer that ranges from 0 to 65535, in milliseconds. The default value is 2000 milliseconds.
-s size	Specifies a 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 100 to 9600.
-g	Performs the test using MPLS fragments.	-
segment-routing	Specifies a segment routing scenario.	-
ip ip-address	Specifies the destination IPv4 address or host name of a BGP LSP.	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. It cannot contain spaces.
mask-length	Specifies the mask length of the destination address.	The value is an integer ranging from 0 to 32.
flex-algo flex-algo-id	Flex-Algo ID. If a Flex-Algo SR-MPLS BE LSP is used, you need to specify flex-algo-id to initiate a test.	The value is an integer that ranges from 128 to 255.
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.	-
bypass	Sets the flag of the backup path.	-
remote remote-ip	Specifies a remote IP address. It is mainly used in the SR-MPLS and LDP tunnel interworking scenario.	The value is in dotted decimal notation.
remote-fec	Indicates the remote FEC type. This parameter is used in scenarios where a device running an earlier version interworks with a device running a later version. This parameter specifies the FEC that can be identified by a device running an earlier version to implement interworking with a device running a later version.	-
ldp remoteipaddr	Specifies the IP address of a remote LDP FEC.	The value is in dotted decimal notation.
remotemasklen	Specifies the mask length of the remote LDP FEC.	The value is an integer ranging from 0 to 32.
sr-te	Specifies the LSP ping type as SR-MPLS TE Policy.	-
policy	Specifies the LSP ping type as SR-MPLS TE Policy.	-
policy-name policyname	Specifies the name of a policy.	The value is a string of 1 to 31 characters.
endpoint-ip endpoint-ip	Specifies the destination IPv4 address of an SR-MPLS TE Policy.	The value is in dotted decimal notation.
color colorid	Specifies the color value of an SR-MPLS TE Policy.	The value is an integer ranging from 0 to 4294967295.
binding-sid bsid	Specifies the ID of a segment to be bound.	The value is an integer that ranges from 16 to 1048575.

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.

The tracert lsp command uses MPLS Echo Request packets and MPLS Echo Reply packets to detect the connectivity of LSPs. Both Echo Request and Echo Reply packets are transmitted in the format of UDP packets through port 3503. The receiver distinguishes these two types of packets based on the port number. An MPLS Echo Request packet carries FEC information to be detected, and is sent along the same LSP as other packets carrying the same FEC information. In this manner, the connectivity of the LSP is checked. Echo Request packets are transmitted to the destination using MPLS, whereas MPLS Echo Reply packets are transmitted to the source using IP.

The tracert lsp command can be used to check links of the following types:

SR-MPLS BE IPv4 Tracert: To test the fault point of an SR-MPLS BE IPv4 tunnel, run the tracert lsp [ -a source-ip | -exp exp-value | -h ttl-value | -s size | -g ] * segment-routing ip ip-address mask-length version draft2 [ remote remote-ip ] command.
SR-MPLS BE tunnel connected with an LDP LSP: To locate a fault point on an SR-MPLS BE tunnel connected with an LDP LSP, run the tracert lsp [ -a source-ip | -exp exp-value | -h ttl-value | -t time-out | -s size | -g ] * segment-routing ip ip-address mask-length version draft2 [ remote remote-ip ] command on the ingress to initiate a tracert test to the egress with the destination address being the LDP LSP.
SR-MPLS BE tunnel connected with an LDP LSP: If the LDP side does not support interworking, to locate a fault point on an SR-MPLS BE tunnel connected with an LDP LSP, run the tracert lsp [ -a source-ip | -exp exp-value | -h ttl-value | -s packet-size | -g | -t time-out ] * segment-routing ip ip-address mask-length version draft2 [ remote-fec ldp remoteipaddr remotemasklen ] command on the ingress to initiate a tracert test to the egress with the destination address being the LDP LSP.
SR-MPLS TE policy LSP tracert: If the type of tunnels to be tested is SR-MPLS TE policy, to test the connectivity of a manually configured SR-MPLS TE policy tunnel, run the ping lsp [ -a source-ip | -exp exp-value | -h ttl-value | -s packet-size | -t time-out | -g ] * sr-te policy { policy-name policyname | endpoint-ip endpoint-ip color colorid | binding-sid bsid } command to initiate a tracert test to the egress.

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 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 Reply 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 Reply 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 Reply packet to the source.
The preceding process proceeds until an MPLS Echo Request packet reaches the destination.
In each probe, when receiving an MPLS Echo Request packet, the device on the last hop replies with an MPLS Echo Reply packet, indicating that the trace test ends. In this manner, the result of each probe is displayed on the source, based on which you can find the path from the source to the destination.

Configuration Impact

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

Example

# Tracert an Flex-Algo SR-MPLS BE IPv4 Tunnel.

<HUAWEI> tracert lsp segment-routing ip 10.4.4.4 32 flex-algo 128
  LSP Trace Route FEC: SEGMENT ROUTING IPV4 PREFIX 10.4.4.4/32 FLEX-ALGO: 128 , press CTRL_C to break.
  TTL    Replier            Time    Type      Downstream
  0                                 Ingress   10.0.0.4/[20099 ]
  1      10.4.4.4            10 ms   Egress

# Tracert an SR-MPLS TE Policy tunnel.

<HUAWEI> tracert lsp sr-te policy policy-name test
LSP Trace Route FEC: Nil FEC, press CTRL_C to break.  
sr-te policy's segment list:
Preference : 300; Path Type: main; Protocol-Origin : local; Originator: 0, 0.0.0.0; Discriminator: 300; Segment-List ID : 1;  Xcindex : 1
TTL   Replier            Time     Type       Downstream  
0                                Ingress    10.1.2.1/[13312 12]  
1     10.1.2.2           63 ms   Transit    10.1.2.2/[12 ]  
2     6.6.6.6            93 ms   Egress

sr-te policy's segment list:
Preference : 400; Path Type: backup; Protocol-Origin : local; Originator: 0, 0.0.0.0; Discriminator: 400; Segment-List ID : 1;  Xcindex : 1
TTL   Replier            Time      Type       Downstream  
0                                Ingress    10.1.2.1/[13312 12]  
1     10.1.2.2           63 ms   Transit    10.1.2.2/[12 ]  
2     6.6.6.6            93 ms   Egress

# Tracert an SR-MPLS BE IPv4 tunnel.

<HUAWEI> tracert lsp segment-routing ip 2.2.2.2 32 version draft2
  LSP Trace Route FEC: SEGMENT ROUTING IPV4 PREFIX 2.2.2.2/32 , press CTRL_C to break.
  TTL    Replier              Time    Type      Downstream
  0                                   Ingress   192.168.1.2/[1001 ]
  1      192.168.1.2          6 ms    Transit   192.168.2.2/[3 ]
  2      192.168.2.2          6 ms    Egress

**Table 1** Description of the **tracert lsp (All views)** command output
Item	Description
TTL	TTL in an MPLS echo request packet. It indicates the number of hops of the tunnel, through which an echo request packet passes.
Replier	Specifies the IP address of the node sending an MPLS echo reply packet.
Time	Specifies the Round-Trip-Time (RTT), in milliseconds.
Type	Specifies the type of a node. The value can be: Ingress node. Transit node. Egress node.
Downstream	Specifies the address and label of a downstream device.
Preference	The preference of path.
Path Type	The types of path: main path / slave path.
Protocol-Origin	Protocol source: pecp. bgp. local. unknown.
Segment-List ID	Segment list ID.
Originator	Indicates the IP address of the end.
Discriminator	Identifier.
XcIndex	Index of Xc.