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13.2.1. Unknown Unicast Forwarding

13.2.1. Unknown Unicast Forwarding​

When a PE receives an MPLS packet from a remote PE, then, after processing the MPLS label stack, if the top MPLS label ends up being a P2MP LSP label associated with an EVPN instance or -- in the case of ingress replication -- the downstream label advertised in the P-tunnel attribute, and after performing the split-horizon procedures described in Section 8.3:

  • If the PE is the designated forwarder of BUM traffic on a particular set of ESIs for the Ethernet tag, the default behavior is for the PE to flood the packet on these ESIs. In other words, the default behavior is for the PE to assume that for BUM traffic it is not required to perform a destination MAC address lookup. As an option, the PE may perform a destination MAC lookup to flood the packet to only a subset of the CE interfaces in the Ethernet tag. For instance, the PE may decide to not flood a BUM packet on certain Ethernet segments even if it is the DF on the Ethernet segment, based on administrative policy.

  • If the PE is not the designated forwarder on any of the ESIs for the Ethernet tag, the default behavior is for it to drop the packet.

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