I have one router 3725 connected with two switches 3560 ,switches connected between itch other,net works under OSPF. On router I have few sub-interfaces F0/0.1 (server 1), F0/0.2 (...) ,F0/1.1 (server 2). When one link between router and switch crashes,switch with crashed link cat rich router throe another switch.Its all work fine?,but I cant understand what the problem with sub-interfaces on the router,when link crashed the status of interface/sub-interfaces is "Ethernet is up,line protocol is down" and all sub-int on this F0/. link become unrichible. How I can backup this?