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This article explains the behavior of MAC limit violations when the same MAC address appears on different switch ports within the same and different VLANs.
Port 1:
config switch interface
edit "port1"
set description ''
set native-vlan 111
set learning-limit 1
set learning-limit-action shutdown
set sticky-mac enable
Port2:
edit "port2"
set description ''
set native-vlan 111
set learning-limit 1
set learning-limit-action shutdown
set sticky-mac enable
Case1: Violation Occurs (Same Port):
- Connect PC1 (MAC1) to port1.
- MAC1 is learned and becomes sticky.
- Remove PC1.
- Connect PC2 (MAC2) to port1 → MAC violation is triggered as expected.
S448ENTF2400xxxx # diagnose switch mac-address list | grep port1
MAC: c4:c6:e6:96:80:dd VLAN: 111 Port: port1(port-id 1)
S448ENTF2400xxxx # get switch mac-limit-violations all
Port VLAN ID MAC Address Timestamp Action
---------------------------------------------------------------------------------------------------------
port1* 111 a4:bb:6d:db:d2:ae 2025-06-20 11:11:40 disable
Note:
Since MAC-2 is the second address on port 1, a MAC violation is triggered, and MAC-2 will not be learned on port 1. So, it is good
Case2: Violation Not Triggered (When MAC 1 is already learnt on port 1):
If PC2 is connected on port 2, MAC2 gets learnt on the port. If PC1 is connected to port2, no new violation is visible:
S448ENTF2400xxxx # diagnose switch mac-address list | grep port2
MAC: a4:bb:6d:db:d2:ae VLAN: 111 Port: port2(port-id 2)
S448ENTF2400xxxx # get switch mac-limit-violations all
Port VLAN ID MAC Address Timestamp Action
---------------------------------------------------------------------------------------------------------
port1* 111 a4:bb:6d:db:d2:ae 2025-06-20 11:11:40 disable
Note:
Since MAC-1 is a static MAC on port 1, port 2 will not add MAC-1 when the PC is connected to port 2. So, violation will not happen. It is expected.
Case3: Violation Occurs (Different VLAN):
If the same steps are repeated but with PCs in different VLANs are violations are seen as expected.
S448ENTF24000xxx # get switch mac-limit-violations all
Port VLAN ID MAC Address Timestamp Action
---------------------------------------------------------------------------------------------------------
port1* 111 a4:bb:6d:db:d2:ae 2025-06-20 10:59:52 disable
port2* 1 c4:c6:e6:96:80:dd 2025-06-20 11:02:39 disable
Note:
The same MAC can be in different VLANs, so the MAC number will exceed 2, and a violation will occur. It is expected.
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