Understanding MAC Pinning
Starting in Junos OS Release 16.1, Junos OS supports MAC pining to prevent loops on the MX series routers. A MAC move occurs when a MAC address frequently appears on a different physical interface than the one it was learned on. Frequent MAC moves indicate the presence of loops in Layer 2 bridges and in virtual private LAN service (VPLS) networks. To avoid loops, you can enable the MAC pinning feature on an interface. The MAC pinning feature is applicable only when dynamic learning of MAC addresses over interfaces is enabled.
When you enable MAC pinning on an interface in a bridge domain or VPLS domain, MAC addresses learned over that interface cannot be relearned on any other interface in the same bridge domain or VPLS domain until the MAC address either ages out on the first interface or is cleared from the MAC table. If a packet with the same MAC address arrives at any other interface in the same bridge domain, it is discarded. This, effectively, controls MAC address moves and prevents the creation of loops in Layer 2 bridges and VPLS domains.
If the timeout interval for the MAC addresses is not specified by setting the mac-table-aging-time statement, the MAC addresses learned over the MAC pinning interface are pinned to the interface until the default timeout period.
You can configure MAC pinning in a bridging environment and in VPLS routing instances. In a bridging environment, you can enable MAC pinning on an access interface and a trunk interface. You can also enable MAC pinning on an access interface or trunk interface of a virtual switch. To avoid loops in the bridging environment, you can use any of the configurations mentioned previously in this topic. To avoid MAC moves and loops, you can use any one of the 16 different MAC pinning configurations.
Starting in Junos OS Release 17.2, the MAC pinning feature is enabled on provider backbone bridging (PBB) and Ethernet VPN (EVPN) integration, including customer edge (CE) interfaces and EVPN over PBB core in both all-active or single-active mode.
To configure MAC pining for PBB-EVPN, include the mac-pinning statement at the [edit routing-instances pbbn protocols evpn], where pbbn is the PBB routing instance over backbone port (B-component). With this configuration, the dynamically learned MAC addresses in the PBB I-component (customer routing instance) bridge domain over CE interfaces, as well as PBB-MPLS core interfaces are pinned. This prevents MAC move on duplicate MAC detection, avoiding loop creation in a network.