One other event can prevent a shortcut from getting established. When the ingress MPC issues the resolution request, the request gets forwarded to the egress MPS. The egress MPS issues a cache imposition request to the egress MPC. If the egress MPC cannot accept a cache imposition, it rejects the imposition request forcing the ingress MPC to continue to use the default paths.
The egress MPC can reject the imposition whenever its local resources prevent it from doing so. For example, the egress MPC might not have enough memory resources to hold another cache entry. It might be that the egress MPC already has too many virtual circuits established and cannot support another circuit. Any of these can cause the egress MPC to reject the imposition preventing a shortcut from getting established.
If you use the MPC debug, you should see a line like that shown at the end of Example 10-19 to confirm that the cache imposition worked
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