If a duplicate MAC address is learned by two different interfaces on an MX Series device, the MAC address learning function correctly flaps between the interfaces. However, the Layer 2 Address Learning Daemon (L2ALD) daemon might crash when attempting to delete the duplicate MAC address when the particular entry is not found in the internal MAC address table. This issue only occurs on MX Series devices with l2-backhaul VPN configured. No other products or platforms are affected by this issue. Affected releases are Juniper Networks Junos OS: 15.1 versions prior to 15.1R7-S1 on MX Series; 16.1 versions prior to 16.1R4-S12, 16.1R6-S6 on MX Series; 16.2 versions prior to 16.2R2-S7 on MX Series; 17.1 versions prior to 17.1R2-S9 on MX Series; 17.2 versions prior to 17.2R1-S7, 17.2R2-S6 on MX Series; 17.3 versions prior to 17.3R2-S4, 17.3R3-S1 on MX Series; 17.4 versions prior to 17.4R1-S5 on MX Series; 18.1 versions prior to 18.1R2 on MX Series.