目标;EIGRP DUAL;EIGRP Successor;EIGRP Feasible Successor;Feasible Successor Route;没有EIGRP的 Feasible Successor;DUAL示例 (开始;DUAL 示例:链路Down;DUAL 示例: D发送查询;DUAL 示例: E发送查询;DUAL示例: C回答;DUAL 示例: E回答;DUAL 示例:收敛