A network includes a RIPv2 domain, an EIGRP domain, and an OSPF domain. Each pair of routing domains has multiple routers redistributing routes between the p air of domains. The design requires that the redistribution configuration avoid matching based on prefix/length because of the trouble in maintaining such configurations. Which one of the following tools can be used in all three routing domains to attem pt to prevent domain loops?（）

A. Setting route tags
B. Setting the default administrative distance differently for internal and external routes
C. Setting administrative distance differently per route
D. Setting metrics much higher for all ext ernal routes than for all internal route