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Cisco Bug: CSCvu04531 - Nexus 3548-XL after upgrading to 7.0(3)I7(7), disabling mac learning is not working

Last Modified

Jul 21, 2020

Products (61)

  • Cisco Nexus 3000 Series Switches
  • Cisco Nexus 3636C-R Switch
  • Cisco Nexus 3548-X Switch
  • Cisco Nexus 3548 Switch
  • Cisco Nexus 9516 Switch
  • Cisco Nexus 3064 Switch
  • Cisco Nexus 31108TC-V Switch
  • Cisco Nexus 92160YC-X Switch
  • Cisco Nexus 3548-XL Switch
  • Cisco Nexus 9396PX Switch
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Known Affected Releases

7.0(3)I7(7) 9.2(2)

Description (partial)

Symptom:
With MAC learning disabled globally and on the interface level we still see MAC is being learnt:

<pre>
STLD1-630.02.02-N3K-RU35(config-if)# show run | i mac
mac-learn disable
  switchport mac-learn disable

STLD1-630.02.02-N3K-RU35(config-if)# show mac address-table
   VLAN     MAC Address      Type      age     Secure NTFY Ports
---------+-----------------+--------+---------+------+----+------------------
*    1     e865.49ee.8101   dynamic  0         F      F    Eth1/10
G    -     b4de.313e.c5fc   static   -         F      F    sup-eth1(R)
G    1     b4de.313e.c5fc   static   -         F      F    sup-eth1(R)
</pre>

Conditions:
We configure the same both "mac-learn disable" under global mode and "switchport mac-learn disable" under interface level" , interface is not learning MAC, everything is fine .

BUT once we configure "no mac-learn disable" and "mac-learn disable" under global mode again, shut/no shut the interface, it triggers the interface starting to learn mac address. The interface flapping can trigger the issue where the interface will start learning the MAC, which is unexpected.

Another trigger is , after we configure "no mac-learn disable" and "mac-learn disable" under global mode again, we then change the traffic from untagged to tagged (or from tagged to untagged) , it also triggers the interface starting to learn mac address.
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