/* 对本接口网段地址的描述*/
link id: 20.0.0.0                              /*网段*/
data : 255.0.0.0                               /*掩码*/
type : StubNet （3）                           /*类型*/
metric : 5                                     /*花费*/

/* 对路由器RTB的描述*/
link id: 2.2.2.2                               /*RTB的router id*/
data : 20.0.0.2                                /*RTB的接口地址*/
type : Router （1）                            /*类型*/
metric : 5                                     /*花费*/