Common troubleshooting common problem via Show Interfaces ?/?

AndreLAndreL Member Posts: 55 ■■□□□□□□□□
I've been looking for this in multipule books but they are all over the place.

Can someone post some common network problem that can be integrated by running a sho int command

Like broadcast storms via - ignored and no buffer

I know there are a lot more than that.

Comments

  • IsmaeljrpIsmaeljrp Member Posts: 480 ■■■□□□□□□□
    Couldn't quite say. I work at a NOC and I can't recall solving an issue with just "show interfaces" specifically.
  • NissekiNisseki Member Posts: 160
    Do you mean when packets are being ignored and duplex issues?
  • CryptoQueCryptoQue PMP, CISSP, CCNP, CCDP, CCNA, CCDA, CCENT, NET+, SEC+, ITILv3 VirginiaMember Posts: 205 ■■■□□□□□□□
    If you're looking at a router, here are a few examples of the many things that can be observed by issuing the "show interface" command:
    - interface operational status (i.e. up, up)
    - bandwidth
    - input and output load
    - input and framing errors that could be from a circuit issue or bad WIC card
  • NetwurkNetwurk Member Posts: 1,155 ■■■■■□□□□□
    I've seen scenarios where a Gig connection was showing only FastEth connectivity

    Full-duplex, 100Mb/s was displayed from the show interfaces output but link should have been Full-duplex, 1000Mb/s

    Turned out to be a bad cable run, using a different run gave us the full Gig speed

    Like others have mentioned, speed and duplex is the most useful info you'll see with the command
  • IsmaeljrpIsmaeljrp Member Posts: 480 ■■■□□□□□□□
    Sorry OP didn't quite get your question there. Most common issue I've seen is duplex and speed mismatches. Also late collisions I've seen quite a few times as we tend to inherit some networks that are built in a way that do not follow standards.
  • Mr.Robot255Mr.Robot255 Member Posts: 196 ■■■□□□□□□□
    From some practice tests these are the common things to look for (icnd1) to my knowledge anyways ,obviously more stuff but i think for icnd1 anyways these are the common things.

    Router
    FastEthernet0/0 is up, line protocol is up (connected)
    Hardware is Lance, address is 0006.2ab4.9c5d (bia 0006.2ab4.9c5d)
    Internet address is 10.10.10.1/24
    MTU 1500 bytes, BW 100000 Kbit, 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 00:00:08, output 00:00:05, output hang never
    Last clearing of "show interface" counters never
    Input queue: 0/75/0 (size/max/drops); Total output drops: 0
    Queueing strategy: fifo
    Output queue :0/40 (size/max)
    5 minute input rate 54 bits/sec, 0 packets/sec
    5 minute output rate 0 bits/sec, 0 packets/sec
    32 packets input, 3607 bytes, 0 no buffer
    Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
    0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
    0 input packets with dribble condition detected
    0 packets output, 0 bytes, 0 underruns
    0 output errors, 0 collisions, 1 interface resets
    0 babbles, 0 late collision, 0 deferred
    0 lost carrier, 0 no carrier
    0 output buffer failures, 0 output buffers swapped out



    Switch

    FastEthernet0/1 is up, line protocol is up (connected)
    Hardware is Lance, address is 000a.41a0.0801 (bia 000a.41a0.0801)
    BW 100000 Kbit, DLY 1000 usec,
    reliability 255/255, txload 1/255, rxload 1/255
    Encapsulation ARPA, loopback not set
    Keepalive set (10 sec)
    Full-duplex, 100Mb/s
    input flow-control is off, output flow-control is off
    ARP type: ARPA, ARP Timeout 04:00:00
    Last input 00:00:08, output 00:00:05, output hang never
    Last clearing of "show interface" counters never
    Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
    Queueing strategy: fifo
    Output queue :0/40 (size/max)
    5 minute input rate 0 bits/sec, 0 packets/sec
    5 minute output rate 0 bits/sec, 0 packets/sec
    956 packets input, 193351 bytes, 0 no buffer
    Received 956 broadcasts, 0 runts, 0 giants, 0 throttles
    0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
    0 watchdog, 0 multicast, 0 pause input
    0 input packets with dribble condition detected
    2357 packets output, 263570 bytes, 0 underruns
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