When will an LSP flap and how do I know that an LSP flap occurred

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If routing flapping or LSP session flapping occurs, LSP flapping occurs. LSPs may also flap when loop detection is configured or address overlapping, multiple links, or ring topologies exist. To determine whether LSP flapping occurs, run the display mpls lsp command to check the number of LSPs. If the number of LSPs frequently changes, LSP flapping occurs. You can also run the snmp-agent trap enable feature-name mpls_lspm command to enable trap for the MPLS LSPM module. If the LSP alarms are frequently generated, LSP flapping occurs. In this case, run the undo snmp-agent trap enable command to restore the default trap settings.

The following alarm information is displayed:
#Jul 25 22:49:18 2020 HUAWEI LSPM/5/TRAP:1.3.6.1.2.1.10.166.2.0.2 LSP 210958 Changes to Down
#Jul 25 22:49:19 2020 HUAWEI LSPM/5/TRAP:1.3.6.1.2.1.10.166.2.0.1 LSP 210958 Changes to Up

Other related questions:
What need I check when LSP flapping occurs
When LSP flapping occurs, check the following information: Whether the peer end can be pinged. Run the display mpls ldp peer command in the system view to check the peer address (Transport-Address field). Run the ping command to check for traffic loss. Whether route flapping occurs. Run the display ip routing-table command in the system view to check all the current routing information. Set the destination address to check all the current routing information mapping the destination address. Frequently check routing information in a period to check for flapping. Whether LDP session flapping occurs. Run the display mpls ldp session command in the system view to check information about all LDP sessions. Set the peer address to check information about the LDP session with the specified peer. Frequently check LDP session information in a period to check for flapping. Whether lsp-trigger all is configured. Whether exceptions occur by enabling the debugging function.

How do I check whether LSP flapping occurs on an AR
You can run the display mpls lsp command to check the number of LSPs. If the number of LSPs changes frequently, LSP flapping occurs. In this case, run the snmp-agent trap enable feature-name mpls_lspm command. If the alarm about LSPs is frequently generated, LSP flapping occurs. Run the undo snmp-agent trap enable command. For example: #Jul 25 22:49:18 2020 HUAWEI LSPM/5/TRAP:1.3.6.1.2.1.10.166.2.0.2 LSP 210958 Changes to Down #Jul 25 22:49:19 2020 HUAWEI LSPM/5/TRAP:1.3.6.1.2.1.10.166.2.0.1 LSP 210958 Changes to Up The preceding information shows that the LSP alternates between Up and Down.

How to configure static LSPs on S series switches
For static LSP configuration on S series switches (except the S1700), see "CLI-based Configuration > Configuration Guide - MPLS > Static LSP Configuration > Configuration Examples > Example for Configuring Static LSPs" in S7700&S9700 V200R010C00 Product Documentation. Configurations on different models are the same, and configurations on the S7700 and S9700 are used as examples.

What is the difference between the static LSP bound to the tunnel and the static CR-LSP
Switches of V200R002C00 or later support the static CR-LSP. A static LSP is classified into the common LSP and static LSP bound to the tunnel. A static CR-LSP must be bound to the tunnel. A static CR-LSP requires bandwidth while a common static LSP does not require.

Do I need to specify the next hop or egress when configuring a static LSP on the ingress node
When configuring a static LSP on the ingress node, ensure that configuration items match routing information, including the destination address, mask, next hop, and outbound interface;otherwise,the LSP cannot become Up. The system calculates the next hop if you specify the outbound interface. The calculated next hop is the IP address of the local outbound interface. The system calculates the outbound interface if you specify the next hop (the inbound interface of the peer end). The calculated outbound interface is still the local outbound interface. Therefore, errors may occur during the static LSP configuration on the ingress node. Pay attention to the following points: If the outbound interface is specified for a static route, you must specify the outbound interface when configuring the static LSP on the ingress node. In other situations, you need to specify the next hop rather than only the outbound interface. The fundamental rule is that the static ingress LSP route fully matches routing information.

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