Common troubleshooting common problem via Show Interfaces ?/?

AndreL

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.

Ismaeljrp

Couldn't quite say. I work at a NOC and I can't recall solving an issue with just "show interfaces" specifically.

Nisseki

Do you mean when packets are being ignored and duplex issues?

CryptoQue

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

Netwurk

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

Ismaeljrp

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.Robot255

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