Examining a CSPF Failure

The ingress router determines the physical path for each label-switched path (LSP) by applying a Constrained Shortest Path First (CSPF) algorithm to the information in the traffic engineering database (TED). This chapter describes a real-world scenario in which the CSPF algorithm fails because of the incorrect association of links with administrative groups (also known as link coloring). It discusses some basic approaches to monitoring and examining a CSPF failure, including how, when, and why you use specific commands. This chapter also includes an examination of an example CSPF log file, traffic engineering database, and corrective action for the example scenario. (See Table 12.)

Table 12: Checklist for Examining a CSPF Failure

Examining a CSPF Failure Tasks
Case Study for a CSPF Failure
Verify That the LSP Is Established	show mpls lsp extensive
Check the Administrative Group Configuration	show configuration protocols mpls show mpls interface show ted database extensive nodeID
Examining a CSPF Failure
Verify the CSPF Failure	clear mpls lsp show mpls lsp extensive
Examine the CSPF Log File	monitor start filename show log filename monitor stop
Examine the Traffic Engineering Database	show ted database extensive For output filtered for color: show ted database extensive nodeID | match "(NodeID | To: | Color)"
Check the Administrative Group Configuration on R5	edit [edit protocols mpls] show delete interface so-0/0/1 admin-group set interface so-0/0/0 admin-group red show commit