300-410 ENARSI: Implementing Cisco Enterprise Advanced Routing and ServicesDemo

Route tags prevent mutual redistribution feedback. Routes redistributed from EIGRP into OSPF at R3 must be assigned tag 1. At R4, the OSPF-to-EIGRP redistribution route map must deny routes matching tag 1 before permitting untagged routes, so a route that originated in EIGRP cannot be injected back into EIGRP. Cisco documents this same tag-and-deny route-map pattern for preventing redistribution loops.