单项选择题IProutingprotocols,suchasOSPFandEnhancedEIGRP,areusedprimarilyinnetworkdesignsthatcontainentryandexitpointstothenetworkfromserviceproviders.WhatisacommontraitofIProutingprotocols?()
A. They add needed overhead in smaller deployments.
B. They are essential for optimum and redundant forwarding.
C. They are used primarily in larger network designs,to support different networks and single entry and exit points.
D. They are usually necessary in smaller deployments.