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LSP Cannot Be Established Due to the Incorrect Configuration of mpls lsp trigger

Publication Date:  2013-09-03 Views:  122 Downloads:  0
Issue Description
After MPLS is enabled on all devices on a MAN and the disp mpls command is executed, the command output shows that no LSP of the loopback address is established on some PE devices (NE40E routers). When some uplinks are disconnected, LSPs are displayed on these NE40Es.

LSPs cannot be established.
Handling Process

Enabled MPLS on relevant interfaces on the PE and P devices to enable the MPLS VPN service.

Check the NE40E configurations onsite and find that the lsp-trigger ip-prefix prefix-name command is configured The user has defined a prefix list that allows only the loopback address of the local device, which causes the fault.

The user thinks that LSP sessions can be globally established after each local loopback address is configured in the prefix list. The lsp-trigger ip-prefix command is incorrectly configured, resulting in LSP establishment failures in ingress and egress of some devices. After some uplinks are disconnected, the NE40E becomes a transit node along an LSP. By default, LDP does not filter routes when establishing an LSP on the transit node. Therefore, some LSPs are displayed.
Root Cause
The lsp-trigger ip-prefix command is incorrectly configured.
On the MAN, only the loopback address of a PE device is a host route with a 32-bit mask. To solve the problem, use the default configuration, that is, the configuration of the lsp-trigger host command. To use a prefix list, define the loopback address segment of all the PE devices in the prefix list.
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