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 routes