How to use Time-Domain Reflectometer (TDR)

[Mohammad Ramadan A.Hafiez]

Hello Guys,

               I have received a call complaining an ip phone down and after checking the logs "phone worked again" I found this log on the 2960 switch...

Controller port error, Interface Gi1/0/5: Power Controller reports power Imax error detected

What does this means? have the employee tried to connect something to this port of the PC port on the phone? what are reasons that a log like this may occure because of.

Notice:

     The logs before this time stamp of the occurence didn't mention any thing aout this port going down because of cable un plugging.

[Mohammad Ramadan A.Hafiez]

Hi Leo

        Ok, I have googled it and it seems my new connected cable is OK,

So, Do u suggest there was a shortage or Open "Cut" in the cable ? if Yes, May be there was, because as we replaced the cable, the phone back working again.

Eletrically, if short circuit occured that will request higher current in the cable from the port --> means requesting more power that can be allocated --> we now get the log above about the max power.

Is this correct?

[Leo Laohoo]

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@Mohammad Ramadan A.Hafiez wrote:

Am not familiar with this command, what does it tell you please?.

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How to use Time-Domain Reflectometer (TDR)

If you connect the phone directly to the switch and keep an eye on it, does the behaviour remain the same?

[Mohammad Ramadan A.Hafiez]

After changing the cable as I've mentioned, The behavior remain the same. "stable".

[Leo Laohoo]

I mean if you connect the phone directly to the switch do you get the same error message?

[Mohammad Ramadan A.Hafiez]

No messages if i connect the phone directly to the switch.

[Leo Laohoo]

Can you post the complete output to the command "sh interface Gi 1/0/5 cont"?

I have a strong suspicion Pair "A" is faulty. The numbers don't match with the rest of the pairs.

[Mohammad Ramadan A.Hafiez]

Ok, I will check the whole cable again, and change the patch cords with another.
Thank you. :)

[Leo Laohoo]

Can you post the complete output to the command "sh interface Gi 1/0/5 cont"? 

[Mohammad Ramadan A.Hafiez]

yes, the output is as follow:
EFTA-2960-3EDGE-18#sh interface Gi 1/0/5 cont
GigabitEthernet1/0/5 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is 00e1.6dbd.0a85 (bia 00e1.6dbd.0a85)
Description: ******** To IP phone ********
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/s, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:06, output 00:00:06, 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
15592307 packets input, 3330139037 bytes, 0 no buffer
Received 123149 broadcasts (106133 multicasts)
0 runts, 0 giants, 0 throttles
8 input errors, 6 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 106133 multicast, 0 pause input
0 input packets with dribble condition detected
17160254 packets output, 3543158646 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

Transmit GigabitEthernet1/0/5 Receive
3543158646 Bytes 3330139037 Bytes
16389797 Unicast frames 15469158 Unicast frames
108026 Multicast frames 106133 Multicast frames
662431 Broadcast frames 17016 Broadcast frames
0 Too old frames 3250218108 Unicast bytes
0 Deferred frames 16870363 Multicast bytes
0 MTU exceeded frames 1103864 Broadcast bytes
0 1 collision frames 0 Alignment errors
0 2 collision frames 6 FCS errors
0 3 collision frames 0 Oversize frames
0 4 collision frames 0 Undersize frames
0 5 collision frames 0 Collision fragments
0 6 collision frames
0 7 collision frames 0 Minimum size frames
0 8 collision frames 769697 65 to 127 byte frames
0 9 collision frames 14822150 128 to 255 byte frames
0 10 collision frames 85 256 to 511 byte frames
0 11 collision frames 304 512 to 1023 byte frames
0 12 collision frames 79 1024 to 1518 byte frames
0 13 collision frames 0 Overrun frames
0 14 collision frames 0 Pause frames
0 15 collision frames
0 Excessive collisions 2 Symbol error frames
0 Late collisions 0 Invalid frames, too large
0 VLAN discard frames 0 Valid frames, too large
0 Excess defer frames 0 Invalid frames, too small
635474 64 byte frames 0 Valid frames, too small
1456175 127 byte frames
14832550 255 byte frames 0 Too old frames
230810 511 byte frames 0 Valid oversize frames
2894 1023 byte frames 0 System FCS error frames
2350 1518 byte frames 0 RxPortFifoFull drop frame
1 Too large frames
0 Good (1 coll) frames
0 Good (>1 coll) frames

[Leo Laohoo]

What happens if you connect the phone, in it's original location, to a different port on the switch?

[Mohammad Ramadan A.Hafiez]

Now the phone in it's original location working fine, I tested it on some other port, then reconnected it again in it's original port and working.