03-09-2016 05:52 PM - edited 03-08-2019 04:54 AM
Hi,
We have a problem connecing a 3850 stack to a pair on N5K. The N5Ks are connected to a pair of N7K. (diagram attached).
When the 3850 is connected, the one of the N5K (B) log shows that a loop was detected on one of the vlans (all VLANs are fine except 27). The mac address are below are the hardware address of the vlan interface.
%FWM-2-STM_LOOP_DETECT: Loops detected in the network for mac d867.d902.3c42 among ports Po10 and Po1 vlan 27 - Disabling dynamic learn notifications for 180 seconds
%FWM-2-STM_LOOP_DETECT: Loops detected in the network for mac 0000.0c9f.f0d9 among ports Po10 and Po1 vlan 27 - Disabling dynamic learn notifications for 180 seconds
The 3850 at the moment are not configured as an etherchannel to the N5K.
Can you advise?
TIA.
PF
03-09-2016 06:57 PM
The ports where the 3850 and Nexus 5k connect - are they all configured the same? For example, all are trunk ports with the same native VLAN?
03-09-2016 07:51 PM
Phillip,
Thanks for the reply.
Yes they are configured the same, same native vlan.
It works fine if the interface to the 3580 on N5K A is disabled. If the interface to the 3850 on N5K B is disabled, we still have the loop issue.
Will configuring a VPC from N5K to the 3850 help or cause any issue?
Thanks.
PF
03-09-2016 07:55 PM
It's not a VPC but a Port-channel you need to configure, and as long as their is a VPC between the 5k's then that is a better solution.
The 3850 will need a corresponding Port-Channel configured as well.
03-09-2016 08:54 PM
Phillip,
The config should be
N5K A
Int e1/25
Channel-group 25 mode active
Int po 25
Vpc 25
N5K B
Int e /25
Channel-group 25 mode active
Int po 25
Vpc 25
3850
Int te1/1/3
Channel-group 25 mode active
Int te3/1/3
Channel-group 25 mode active
If I didn’t have the vpc 25 on port-channel 25, the system will automatically create a random vpc id.
ie
Sh vpc
vPC status
----------------------------------------------------------------------------
id Port Status Consistency Reason Active vlans
------ ----------- ------ ----------- -------------------------- -----------
264064 Po1921 up success success 2-4,6-15,13
,248,512....
Is the above not right?
Thanks.
PF
03-09-2016 09:29 PM
The above looks good to me!
03-14-2016 05:49 PM
Thanks Phillip.
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