Cisco 4948E: Short Disconnection Issue

[tmq626]

Hi guys,

I have 3 Cisco 4948E switches in 3 cabinets. They have been working greatly, but one switch recently has short disconnection issue. About 20,000 packets, it has 7 packets loss at the same time and caused around 30 seconds disconnection on the servers. It happened 3-4 times a day. This switch has 10Gbps uplink and serving less than 500Mbps.

My other two switches in same vlan don’t have this short disconnection issue.

I have tried to reseat the uplink on both sides, but it didn't help.

Do you guys have any ideas what may caused this short disconnection?

Thank you for your time!

Tom

[Georg Pauwen]

Hello Tom,

can you post the output of 'show interfaces' for the uplink ports ?

The issue could either be physical (cabling etc.), spanning tree or other configuration related, or some sort of bug. Post the output of 'show version' as well...

[tmq626]

Hi Georg,

Here is "show interface" of the uplink port:

---

TenGigabitEthernet1/49 is up, line protocol is up (connected)
Hardware is Ten Gigabit Ethernet Port, address is 7cad.7400.0370 (bia 7cad.7400.0370)
MTU 1500 bytes, BW 10000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 4/255, rxload 5/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 10Gb/s, link type is auto, media type is 10GBase-LR
input flow-control is on, output flow-control is off
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output never, output hang never
Last clearing of "show interface" counters 5d07h
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 216438000 bits/sec, 24726 packets/sec
5 minute output rate 172526000 bits/sec, 22250 packets/sec
8795656133 packets input, 7589755262701 bytes, 0 no buffer
Received 29180470 broadcasts (10197488 multicasts)
0 runts, 0 giants, 0 throttles
8 input errors, 8 CRC, 0 frame, 0 overrun, 0 ignored
0 input packets with dribble condition detected
10025604683 packets output, 10337516054997 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out

---

Show Version:

---

Cisco IOS Software, Catalyst 4500 L3 Switch Software (cat4500e-ENTSERVICESK9-M), Version 15.1(2)SG7, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2015 by Cisco Systems, Inc.
Compiled Tue 01-Dec-15 13:30 by prod_rel_team

ROM: 12.2(44r)SG11
C4948E uptime is 29 weeks, 5 hours, 10 minutes
System returned to ROM by power-on
System image file is "bootflash:cat4500e-entservicesk9-mz.151-2.SG7.bin"
Hobgoblin Revision 21, Fortooine Revision 1.40

Last reload reason: power-on

This product contains cryptographic features and is subject to United
States and local country laws governing import, export, transfer and
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Importers, exporters, distributors and users are responsible for
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agree to comply with applicable laws and regulations. If you are unable
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http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to
export@cisco.com.

cisco WS-C4948E (MPC8548) processor (revision 8) with 1048576K bytes of memory.
Processor board ID CAT1709S376
MPC8548 CPU at 1GHz, Cisco Catalyst 4948E
Last reset from PowerUp
2 Virtual Ethernet interfaces
48 Gigabit Ethernet interfaces
4 Ten Gigabit Ethernet interfaces
511K bytes of non-volatile configuration memory.

Configuration register is 0x2102

---

Btw, my other Cisco 4948E is using this same ios version file and do not have this disconnection issue.

Thanks,

Tom

[tmq626]

I just noticed from the show interface, it has "8 input errors, 8 CRC, 0 frame, 0 overrun, 0 ignored" while the uplink of my other two switches have 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored.

I am not sure if this is the issue?

Thanks,

Tom

[Georg Pauwen]

Hello Tom,

you have (very few) CRC and input errors on your interface, since the amount of both is exactly the same, your issue is most likely related to a physical problem. Try, if possible, to replace the cabling, or (depending on the model you have) reinsert the SFPs.

[tmq626]

I have tried to swap a new Cisco SFP-10G-LR module and still had short disconnection. I noticed the show interface reported 10Gbps uplink increased input errors and CRC from 8 to 9:

---

TenGigabitEthernet1/49 is up, line protocol is up (connected)
Hardware is Ten Gigabit Ethernet Port, address is 7cad.7400.0370 (bia 7cad.7400.0370)
MTU 1500 bytes, BW 10000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 8/255, rxload 2/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 10Gb/s, link type is auto, media type is 10GBase-LR
input flow-control is on, output flow-control is off
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output never, output hang never
Last clearing of "show interface" counters 6d11h
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 114095000 bits/sec, 26465 packets/sec
5 minute output rate 316277000 bits/sec, 31840 packets/sec
11119970108 packets input, 9340299753193 bytes, 0 no buffer
Received 35665474 broadcasts (12418768 multicasts)
0 runts, 0 giants, 0 throttles
9 input errors, 9 CRC, 0 frame, 0 overrun, 0 ignored
0 input packets with dribble condition detected
12340696808 packets output, 12776017459503 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out

---

So, the optics should be the culprit?

Thanks,

Tom

[Georg Pauwen]

Tom,

cabling could be the issue as well. Follow the entire cable run end to end. As stated, CRC and input errors are almost always layer 1 related...

[tmq626]

Georg,

It's increased to 11 input errors 11 crc, but I only got 1 disconnection today (not 3-4 times like other days).

What do you mean layer 1 related? In the previous post, you said it is most likely related to a physical problem.

Thanks,

Tom

[Georg Pauwen]

Hello Tom,

physical problem = layer 1.

Sorry for the misunderstanding. Physical problems are layer 1 problems (based on the OSI model).

That said, even 1 disconnect is one too many. Did you check the entire cable run (including wiring closet connectors) ?