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virtual interface sometimes freezes


Virtual interface in WS-C3850-12S is often freezes. And there are no log messages about it. Traffic is always minimum so I don't see any obvious reasons for it. The network which is concerns to this interface is not avaliable at that moment. I do "shut down" and "no shut down" for this interface and then it is going to recovery. SW version is 03.07.05E.

5 Replies 5



post the output of 'show interfaces vlan x' where 'x' is the virtual interface that freezes...

Router#sho interfaces vla 114
Vlan114 is up, line protocol is up
Hardware is Ethernet SVI, address is 0041.d213.bcec (bia 0041.d213.bcec)
Internet address is
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 not supported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output never, 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 314000 bits/sec, 258 packets/sec
5 minute output rate 320000 bits/sec, 227 packets/sec
2187057641 packets input, 314763334272 bytes, 0 no buffer
Received 0 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
1302666180 packets output, 244420231713 bytes, 0 underruns
0 output errors, 7 interface resets
1 unknown protocol drops
0 output buffer failures, 0 output buffers swapped out

Do you have 10G modules installed by any chance ? There is a bug related to that. Can you post the output of 'show version' ?

Yes, there are two 10g modules in te1/1/4, te2/1/4.


Router#sh ver
Cisco IOS Software, IOS-XE Software, Catalyst L3 Switch Software (CAT3K_CAA-UNI
ERSALK9-M), Version 03.07.05E RELEASE SOFTWARE (fc1)
Technical Support:
Copyright (c) 1986-2017 by Cisco Systems, Inc.
Compiled Fri 10-Feb-17 07:59 by prod_rel_team


Cisco IOS-XE software, Copyright (c) 2005-2015 by cisco Systems, Inc.
All rights reserved. Certain components of Cisco IOS-XE software are
licensed under the GNU General Public License ("GPL") Version 2.0. The
software code licensed under GPL Version 2.0 is free software that comes
with ABSOLUTELY NO WARRANTY. You can redistribute and/or modify such
GPL code under the terms of GPL Version 2.0.
( For more details, see the
documentation or "License Notice" file accompanying the IOS-XE software,
or the applicable URL provided on the flyer accompanying the IOS-XE



Router_ASDUE uptime is 34 weeks, 3 days, 2 hours, 40 minutes
Uptime for this control processor is 34 weeks, 3 days, 2 hours, 44 minutes
System returned to ROM by Power Failure
System restarted at 14:32:31 msk Tue Oct 3 2017
System image file is "flash:packages.conf"
Last reload reason: Power Failure


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License Level: Ipservices
License Type: Permanent
Next reload license Level: Ipservices

cisco WS-C3850-12S (MIPS) processor with 4194304K bytes of physical memory.
Processor board ID FCW1945C0G1
30 Virtual Ethernet interfaces
32 Gigabit Ethernet interfaces
8 Ten Gigabit Ethernet interfaces
2048K bytes of non-volatile configuration memory.
4194304K bytes of physical memory.
250456K bytes of Crash Files at crashinfo:.
250456K bytes of Crash Files at crashinfo-2:.
1609272K bytes of Flash at flash:.
1609272K bytes of Flash at flash-2:.
0K bytes of Dummy USB Flash at usbflash0:.
0K bytes of Dummy USB Flash at usbflash0-2:.
0K bytes of at webui:.

Base Ethernet MAC Address : 00:41:d2:13:bc:80
Motherboard Assembly Number : 73-15839-07
Motherboard Serial Number : FOC19449J86
Model Revision Number : H0
Motherboard Revision Number : B0
Model Number : WS-C3850-12S
System Serial Number : FCW1945C0G1

Switch Ports Model SW Version SW Image Mode
------ ----- ----- ---------- ---------- ----
* 1 20 WS-C3850-12S 03.07.05E cat3k_caa-universalk9 INSTALL
2 20 WS-C3850-12S 03.07.05E cat3k_caa-universalk9 INSTALL

Switch 02
Switch uptime : 34 weeks, 3 days, 2 hours, 52 minutes
Base Ethernet MAC Address : 00:41:d2:59:85:80
Motherboard Assembly Number : 73-15839-07
Motherboard Serial Number : FOC19449J6H
Model Revision Number : H0
Motherboard Revision Number : B0
Model Number : WS-C3850-12S
System Serial Number : FCW1945D0FS

Configuration register is 0x102



here is the bug. Since you also see the 'unknown protocol drops' this bug could be the problem. The solution is to upgrade or downgrade to:




SVI on 3850 will fail to ping after one/more reload(s)
After a reload of 3850, one/more SVI's would not be reachable when traffic passes through tenGig interfaces of C3850-NM-2-10G module. All dropped packets are accounted to "unknown protocol drops" of the interface that traffic ingresses on.

LULU#show inter te1/1/3 | in unknown
21 unknown protocol drops

YOJIMBO#ping rep 10
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:
## Sent 10 pings and all failed. All accounted to uknown protocol drops.

LULU#show inter te1/1/3 | in unknown
31 unknown protocol drops ----------------- Unknown protocol drops increment by 10

Seen only after one/more reload(s)

remove and reconfigure the affected SVI

no interface vlan <>
interface vlan <>

Further Problem Description:
Only ingress traffic is impacted, egress traffic goes through fine

Layer-3 interface created on physical port will not impacted as well.
Only traffic destined to SVI is affected.
Flow-through/hw-switched traffic is NOT impacted.
CDP/STP traffic is also NOT impacted.

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