Port Flapping Issue

[PolarPanda]

Hi there,

        According to syslog, one port of one of our switches keeps flapping. Goes up and down. The end device of the port is a sharp printer. I tried to change cable and hard code speed to match printer setting. Do you have similar issue and know the solution? Is it possible that printer lose network connection during deep sleep? Thank you.

[Leo Laohoo]

Post the complete output to the command "sh interface <PORT>".
Plug a laptop on the same port and see if the port flaps or not.

[PolarPanda]

The printer in a different location and cannot be unplugged during business hours, so I might test the port with different device later.

I realized that the output of the command still shows half duplex, event I literally typed in duplex full in the interface config. So it looks like it changed back to half duplex after the interface back up from down status. It showed full duplex before the interface went down. After it's back up for a while, it changed to full duplex again. so confused.

Here is the result of the command:

GigabitEthernet1/0/2 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is xxxxxxxxxxx
Description: User Vlan
MTU 1500 bytes, BW 10000 Kbit/sec, DLY 1000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Half-duplex, 10Mb/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 00:00:22, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: Class-based queueing
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 3000 bits/sec, 4 packets/sec
682224 packets input, 234593450 bytes, 0 no buffer
Received 74175 broadcasts (62048 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 62048 multicast, 1 pause input
0 input packets with dribble condition detected
13951352 packets output, 1888620167 bytes, 0 underruns
56 output errors, 26 collisions, 1 interface resets
2566 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

[pieterh · Accepted solution]

>>> Is it possible that printer lose network connection during deep sleep? <<<

YES it is! Also workstations can show that behavior.

if possible you can search how to disable the network interface from power saving.

alternatively you can disable link up/down messages from the log in interface configuration mode

      "no logging event link-status"

[paul driver]

Hello

Change speed/duplex to auto negotiate on the printer and the access port test again.