CISCO switch usage tips

The full duplex of a CISCO switch means that the switch can receive data while sending data. The two are synchronized, and its performance far exceeds the forwarding performance between common Bridging networks, I have accumulated some experience in using CISCO switches and hope to provide some reference to my friends.

I believe many network administrators and friends have encountered such a problem: that is, when the CONSOLE port of a CISCO switch is connected to a serial port to debug the switch (except for the first time configuring the switch, most of them are due to switch faults and cannot be logged on through the network port ).

At this time, it is often 100,000 in a rush, but the more urgent it is, the more difficult it is to make a command than to log on to the sky, because the configuration interface opened by the super terminal will be from time to time (or non-stop) some system prompts are displayed. At this time, the command input will be completely disrupted.

That is to say, you cannot enter a complete string of commands in one line. At that time, it was a test of the psychological quality of the network administrator and the keyboard-based fingering method. It can be described by typing commands with your eyes closed, after the command is completed, it is expected that the error will be eliminated and so many error messages will not be displayed (of course, it will not succeed in ).

What does this mean? When we debug a CISCO switch, it is inevitable that we will enter an incorrect command, for example, if we type one more letter or one less letter, I thought the switch would prompt this command error, but a strange thing happened at this time. The system didn't prompt us for a command error, but made a connection to it (that is, the command was executed the same ), as follows:

 
 

  
  
3550#show ip interface brief  
  
  
 
  
  
Interface IP-Address OK? Method Status Protocol  
  
  
 
  
  
Vlan1 unassigned YES NVRAM administratively down down  
  
  
 
  
  
Vlan2 172.19.96.1 YES NVRAM up up  
  
  
 
  
  
FastEthernet0/1 unassigned YES unset up up  
  
  
 
  
  
FastEthernet0/2 unassigned YES unset up up  
 
 

That is to say, the switch considers the incorrect command as the host name and tries to resolve it by querying the DNS server. If the DNS server is set on the switch, the progress will be faster. If there is no DNS server, the progress will be slow. How can we avoid this situation? Enter the following command:

 
 

  
  
3550#show ip interface brief | i Fast  
  
  
 
  
  
FastEthernet0/1 unassigned YES unset up up  
  
  
 
  
  
FastEthernet0/2 unassigned YES unset up up  
  
  
 
  
  
FastEthernet0/3 unassigned YES unset up up  
 
 

As a network administrator, when we access a new service on a vswitch, we always need to first find an idle port on the vswitch, configure the necessary service, and then connect the network cable, however, when there are many cables on the vswitch, it is difficult to identify the idle port accurately with the naked eye, so we used to log on to the vswitch and run the following command to view the problem:

 
 

  
  
3550#show ip interface brief | i Fast  
  
  
 
  
  
FastEthernet0/1 unassigned YES unset up up  
  
  
 
  
  
FastEthernet0/2 unassigned YES unset up up  
  
  
 
  
  
FastEthernet0/3 unassigned YES unset up up  
 
 

The above three points are some of the experience accumulated by Xiangzi in learning to use CISCO switches. I hope to provide some reference to my friends and open up the fog of faults to identify the real causes of network faults.

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