Unaffiliated Arccus Juniper Networks Bloomberg LP There are a variety of BGP-enabled services in which the originator of a BGP route may attach one or more "Route Targets" to the route. By means of a procedure known as "RT Constrained Distribution" (RTC), a given BGP speaker (call it "B") can announce the set of RTs in which it has interest. The implication is that if a particular route (call it "R") carries any RTs at all, BGP speaker B wants to receive route R if and only if B has announced interest in one of the RTs carried by R. However, if route R does not carry any RTs at all, prior specifications do not make it clear whether B's use of RTC implies that it does not want to receive route R. This has caused interoperability problems in the field, as some implementations of RTC do not allow B to receive R, but some services presuppose that B will receive R. This document updates RFC 4684 by clarifying the effect of the RTC mechanism on routes that do not have any RTs.