02-28-2017 05:04 AM - edited 03-08-2019 09:32 AM
Hey all!
I have a problem where I don't know how to solve it.
I have two Catalyst 4500 as a VSS.
Furthermore, I have a stack of two Catalyst 3850 switches connected to the VSS:
the 3850 stack is connected with two trunk interfaces, as a port-channel.
configuration on the VSS:
interface TenGigabitEthernet1/1/9
switchport mode trunk
switchport nonegotiate
channel-group 22 mode active
interface TenGigabitEthernet2/1/9
switchport mode trunk
switchport nonegotiate
channel-group 22 mode active
configuration on the stack:
interface TenGigabitEthernet1/1/1
switchport mode trunk
switchport nonegotiate
ip arp inspection trust
storm-control broadcast level 30.00
storm-control multicast level 20.00
storm-control action trap
channel-group 22 mode active
ip dhcp snooping trust
interface TenGigabitEthernet2/1/1
switchport mode trunk
switchport nonegotiate
ip arp inspection trust
storm-control broadcast level 30.00
storm-control multicast level 20.00
storm-control action trap
channel-group 22 mode active
ip dhcp snooping trust
Every minute, I get a syslog message with mac flapping:
Host 685b.3584.bc41 in vlan 20 is flapping between port Te2/1/1 and port Po22 (Access-2-2-2)
That's just an example, there are other message with other mac addresses and other vlans.
Is someone able to help me?
Thanks!
02-28-2017 08:49 AM
Hi,
Can you post the output of 'show etherchannel summary' from the Cisco 4500 and 3850 switches?
Thanks
02-28-2017 11:10 PM
Hi,
that's normal:
Group Port-channel Protocol Ports
------+-------------+-----------+-----------------------------------------------
22 Po22(SU) LACP Te1/1/1(P) Te2/1/1(P)
They are both bundled.
02-28-2017 11:36 PM
This looks like a bug with the Cisco Catalyst 3850 switch
MAC address being learnt on an individual Port-channel member interface
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCut87285
03-01-2017 12:19 AM
Oh okay thanks!
I will try an ios update and keep you posted.
02-28-2017 09:05 AM
Hi
It could be generated by a loop on somewhere, you should identify what kind of device are associated to the MAC addresses displayed on the logs, you can use:
show mac address-table | include <mac address or at least the last 4 values>
Also it could be a wireless client.
This link could be useful:
https://blogs.it.ox.ac.uk/networks/2011/02/04/mac-flaps-why-are-they-bad/
:-)
02-28-2017 11:15 PM
There is no loop.
And it isn't a wireless client.
Our VSS is in the middle of our star toplogy and all access switches around it.
I have those mac flappings on all access switches.
But the weird thing is: Why is it flapping between the portchannel interface and the psyhical portchannel interface. That makes so sense.
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