Explore in detail the Cisco router global debugging method

There are a lot of users using Cisco routers, So I studied the global debugging of Cisco routers and shared it with you here. I hope it will be useful to you. When configuring a Cisco router, the boundaries between global and interface commands are obvious. In this case, we use "Global" to identify commands that cannot be used for interface debugging or specific transmission media types and Protocol debugging.

For example, in the 2500 series Cisco routers, you can use Debugging commands to analyze the Cisco Discovery Protocol (CDP ). We remotely log on to the Cisco router through telnet. By default, the output of the DEBUG command is sent to the console. If it is in a telnet session, we can use the terminal monitor command to view the output.

Interface debugging

The debug serial interface command is a debugging command directly related to the Cisco router interface and transmission media type. In the following example, the serial interface is encapsulated by HDLC. End-to-End HDLC keeps Active packets exchanged every 10 seconds. This indicates that the link operation is normal and the Layer 2 operation is normal. The show interface serial0 command indicates that the line protocol is started normally. Use the undebug all command to disable all debugging tasks.

Protocol debugging

The following are two examples of protocol debugging. Both examples are related to the IP protocol. Of course, the DEBUG command applies to all other protocols. The first example (as shown below) shows ARP debugging. ARP Debugging starts, then clears the ARP cache, and generates ARP requests and responses. First, we use the command to clear all ARP caches on the Cisco router. Therefore, each LAN segment connected to the Cisco router generates an ARP packet. Because we do not need to generate too many ARP packets, the selected Cisco router is connected to only one Ethernet segment.

The second example (as shown below) shows ip rip debugging. The Cisco router table was not cleared at the beginning of the debugging. Because the Router performs a RIP update every 30 seconds, you do not need to force update. Similar to the first example, all debugging tasks should be disabled after sufficient information is obtained.