文件名称：接口的几种状态－诊断的步骤-CCNA中文版PPT
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更新时间：2024-05-15 11:39:26
CCNA
接口的几种状态－诊断的步骤 * Purpose: This slide explains how to interpret the show interfaces serial command output. Emphasize: The show interfaces serial command output indicates that the serial interface is up and the line protocol is up. The first parameter refers to the hardware layer and essentially reflects whether the interface is receiving the Carrier Detect signal from the other end. The second parameter refers to the data link layer. This parameter reflects whether the data link layer protocol keepalives are being received. If both the interface and the line protocol are up, the connection is operational. If the hardware is up and the line protocol is down, a connection problem exist such as no clocking, wrong encapsulation type, or no keepalives. If both the line protocol and the interface are down, a cable might never have been attached to the router. On the serial cable, you can plug in the cable upside-down, causing the pins on the serial cable to break. There is one more possibility. If the information says “administratively down,” you have manually disabled (shut) the interface. Cisco offers a hardware class (IMCR) that discusses the router hardware in more detail.