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13.1. Forwarding Packets Received from a CE

13.1. Forwarding Packets Received from a CE​

When a PE receives a packet from a CE, on a given Ethernet Tag ID, it must first look up the source MAC address of the packet. In certain environments that enable MAC security, the source MAC address MAY be used to validate the host identity and determine that traffic from the host can be allowed into the network. Source MAC lookup MAY also be used for local MAC address learning.

If the PE decides to forward the packet, the destination MAC address of the packet must be looked up. If the PE has received MAC address advertisements for this destination MAC address from one or more other PEs or has learned it from locally connected CEs, the MAC address is considered a known MAC address. Otherwise, it is considered an unknown MAC address.

For known MAC addresses, the PE forwards this packet to one of the remote PEs or to a locally attached CE. When forwarding to a remote PE, the packet is encapsulated in the EVPN MPLS label advertised by the remote PE, for that MAC address, and in the MPLS LSP label stack to reach the remote PE.

If the MAC address is unknown and if the administrative policy on the PE requires flooding of unknown unicast traffic, then:

  • The PE MUST flood the packet to other PEs. The PE MUST first encapsulate the packet in the ESI MPLS label as described in Section 8.3. If ingress replication is used, the packet MUST be replicated to each remote PE, with the VPN label being an MPLS label determined as follows: This is the MPLS label advertised by the remote PE in a PMSI Tunnel attribute in the Inclusive Multicast Ethernet Tag route for a <MAC-VRF> or <MAC-VRF, Ethernet tag> combination.

The Ethernet tag in the route may be the same as the Ethernet tag associated with the interface on which the ingress PE receives the packet. If P2MP LSPs are being used, the packet MUST be sent on the P2MP LSP of which the PE is the root, for the Ethernet tag in the EVPN instance. If the same P2MP LSP is used for all Ethernet tags, then all the PEs in the EVPN instance MUST be the leaves of the P2MP LSP. If a distinct P2MP LSP is used for a given Ethernet tag in the EVPN instance, then only the PEs in the Ethernet tag MUST be the leaves of the P2MP LSP. The packet MUST be encapsulated in the P2MP LSP label stack.

If the MAC address is unknown, then, if the administrative policy on the PE does not allow flooding of unknown unicast traffic:

  • the PE MUST drop the packet.
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