This article describes RSVP Label Switched Path (LSP) optimization behavior in an inter-domain setup.

The RSVP LSPs formed over a multi-area OSPF using an inter-domain knob as shown below under the configuration hierarchy will not support automatic re-optimization of LSP paths when a best path becomes available.

lab@R1> show configuration protocols mpls 
label-switched-path to_R5 {
    to 192.168.1.5;
    optimize-timer 30;
    inter-domain;
    adaptive;
}

By default, LSP re-optimization to best path happens as per the configured or default optimization interval for a specified LSP. However, in the case of an inter-domain set up, you will be required to manually clear the label switched path by using the command clear mpls lsp <lsp-name> for the LSP to select the newly available best path.

At this time, it can be observed that the LSP and IGP paths are different.

2021-02-19: Article reviewed for accuracy; article accurate and valid