Hi netpro :
I have a problem .in the illustration.The first solution :I config the router A and switch A and B running rapid pvst ,the switch A is root,and switch B is seconder root ,if the black link or red link is broken , convergence is less 1 second.
The second solution: I'll config the Router A interface P1,P2 and Switch A interface P1 P2,SwitchB interface P1,P2 running dynamic routing protocl (ospf or eigrp). beacause of I read the doc ,cisco recommend using L3 routing protocol.
whatever , which is the best solution about this topology ? please help me ,thanks