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Troubleshooting devices on a 3560G switch

houston1910
Level 1
Level 1

Im pretty sure its the same on any cisco switch, but what are some basic commands I could use to troubleshot how much traffic is going and coming to a specific port on the switch. ( the back story ) I had an issue where my network kept bouncing and I could not figure out what device was causing this issue. My Cisco Skills are getting better but still not as strong to do some real in depth troubleshooting. In the past all ive ever done is doing basic functions on switches. In my current role I will be managing them more personally. If theres a thread someone could post that I could read and get better at some good troubleshooting techniques or commands, thats would really help.

Im trying to go for my CCNA, I know that this will help me out.

Cheers!

3 Replies 3

Collin Clark
VIP Alumni
VIP Alumni

Some vry basic ways are to look at the interface statistics. You can do that by typing show interface [interface name]. Here's an example.

  Hardware is EtherSVI, address is 0021.a0e8.ee3a (bia 0021.a0e8.ee3a)
  Description: LAN Segment
  Internet address is 192.168.13.254/24
  MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output never, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/17/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 538000 bits/sec, 72 packets/sec
  5 minute output rate 38000 bits/sec, 38 packets/sec
     124774843 packets input, 2758120790 bytes, 0 no buffer
     Received 1067491 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     100835630 packets output, 3995078729 bytes, 0 underruns
     0 output errors, 1 interface resets
     425871 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out

The area in red shows the load. You can take the 1st number, divide it by the second, then multiply by 100 to get the rough utilization of the port.

1/255=.0039 x 100=.03921% utlization. As you can see this is very low utilization.

The blue area shows the line rate of the interface.

Hope it helps and good luck on the CCNA.

   My personal favorite on these switches is "show controllers utilization" , show the utilization of every port on the switch along with how busy the backplane is .  Show int status , show int counters and show int counters errors are also good onbes to use.

That's a good one Glen. Never knew about it.

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