下面哪个是正确的配置默认路由default route的命令?
A.route ip 172.0.0.0 255.0.0.0 0.0.0.0
B.ip route 0.0.0.0 0.0.0.0 172.16.20.1
C.ip route 0.0.0.0 255.255.255.255 172.16.20.1
D.route ip 0.0.0.0 0.0.0.0 172.16.10.0
正确答案是B