12-01-2021 09:41 AM
Hello Everyone,
We could see there is a packet loss to the access switch. I will say the setup below. Please help me to fix this issue.
Core switch(6504) [Gi1/3/8 & Gi2/3/8]<--> [Gi1/1/1 & Gi1/1/2] 3850 Access Switch[Gi1/0/48] <--> [Gi0/47]Downlink Switch
This is the setup. Note connectivity between Core switch and access switch is Fiber link. and there is no Port-channel configured. Then i could see Loopguard enabled globally in access switch and getting Loopguard blocking and unblocking alerts continuously.
I have tried shut one of the uplink in Core switch. Like Gi1/3/8 and traffic passed via Gi2/3/8 still faced same issue. Packet loss. Vice versa same issue. Then verified the Transceiver details in interfaces no alarm or issue or error on fiber link. Please help me on this.
Regards,
Chandhuru
12-01-2021 10:42 AM
Where is the packet loss you see, end device side ? or gateway ?
Can you post the relavant config of Cat 6504 and Cat 3850 (if the no port-channel configured) how is these 2 Links connected using Trunk ?
Then that where i see the issue, is there any reason for that as trunk ? since there is Loop so you see block and unblock ports due to some convergence in network (this is my assumptions)
Also can you post the logs you see that block and unblock Logs here ?
show version
show run interface gi 1/3/8
show run interface gi 2/3/8
show interface gi 1/3/8
show nterface gi 2/3/8
same information from Cat 3850
12-01-2021 11:13 AM
Thanks for the update Balaji!!!
Where is the packet loss you see, end device side ? or gateway ? Access Switch and downlink Switch
Can you post the relavant config of Cat 6504 and Cat 3850 (if the no port-channel configured) how is these 2 Links connected using Trunk ? Attached log file
Then that where i see the issue, is there any reason for that as trunk ? since there is Loop so you see block and unblock ports due to some convergence in network (this is my assumptions) Yes you are right but if i shut one uplink in core switch also seeing same drops and same issue
Also can you post the logs you see that block and unblock Logs here ? Attached in word file
12-02-2021 01:11 PM - edited 12-02-2021 01:21 PM
Looks you have too much QOS Configuration configured on the Interface. and also i see some Drops on the interface not major.
For testing - Take one of the interface default the interface config, make it simple config and test it is good idea as below :
On Core switch remove cable 2/3/8
config t
!
default int gi2/3/8
interface GigabitEthernet2/3/8
description Uplink to Access Switch
switchport
switchport mode trunk
no shutdown
!
on the access side :
config t
!
default interface GigabitEthernet1/1/2
!
interface GigabitEthernet1/1/2
description *Uplink to Core Swt 2*
switchport mode trunk
no shutdown
end
Now connect the cable between these devices, remove connection from Core Gi 1/3/8
what is the out come ? (based on the results we fine tune the requirements.
Attached in word file
this is missing here can you update the post, let me read the logs
12-03-2021 04:35 AM
Thanks Balaji!!!
Attached here as well log file
Can we expect any Bug on this? Because switch is currently running on 3.2.2.
I will try the suggestion as you said. I dont think it is fix. Because same setup for 2 more switches those are not seeing any latency. Same interface config with same Qos. Anyway let me try as you said. and keep you posted.
12-04-2021 05:24 PM
Hi Friend,
still face issue here ?
if yes then can you check downlink SW elect as root for this domain, Access SW see new root and this make port "loop guard" error.
please make Core SW priority prefer than that of downlink SW and see result.
12-09-2021 07:18 AM - edited 12-09-2021 07:22 AM
Sorry for the delay response!!! Thanks for the reply MHM!!!
Issue has been resolved now!!!
Looks like switch was hit with BUG. Because we tried rebooting the switch has fixed the issue. Now we are not seeing the LOOPGUARD error on logs.
Note: Not sure the BUG details. We suspecting unknown BUG. If anyone aware of this BUG details. Please share.
Switch Model: Cisco 3850
Version: 3.2.2
Regards,
Chandhuru
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