四台路由器R1、R2、R3和R4顺序相连,R1和R4上创建Loopback0接口,接口地址分别为1.1.1.1和 4.4.4.4,四台设备分别配置静态路由协议,保 证R1和R4的Loopback0地址路由可达,R1和R4间建立GRE Tunnel,查看R1上Tunnel接口信息如下: [R1]displa interface Tunnel O Tunnelo current state: UPTunnelo current statle: UP Line protocol current state: UP Description: Tunnel 0 Interface The Maximum transmit Unit is 1476 Internet Addess is 10.1.1.1/30 Primar . Encapsulation isTUNNEL aggregation ID not set Tunnel source l.1.1.1 destination 4.4.4.4 Tunnel keeepalive disable Tunnel protocol/transport GRE/IP. GRE key disable Checksumming of GRE packets disabled 此时,若中断R2和R3之间链路,则下列说法正确的是____
A. R1上的-Tunnel接口保持UP状态
B. R1上的Tunnel接口状态DOWN
C. R4的Tunnel接口IP地址应为10.0.0.2
D. R4的 Tunnel接口的源lP为4.4.4.4,目的lP为 1.1.1.1