300-510 SPRI: Implementing Cisco Service Provider Advanced Routing Solutions

XR3 is the Level 2-to-Level 1 boundary toward XR1, so it must apply the policy to propagate level 2 into level 1. The policy drops the matching 10.33.33.33/32 prefix and explicitly passes all other routes. IOS XR route policies otherwise have an implicit drop disposition, making an explicit else pass necessary to retain nonmatching prefixes.