EVPN-ETREE Overview

The EVPN-ETREE service is a VPN service where each attachment circuit is designated as either root or leaf. The EVPN E-Tree feature implements E-Tree service as defined by the Metro Ethernet Forum (MEF) in draft-sajassi-l2vpn-evpn-etree-03. The E-Tree service is a rooted-multipoint service that is supported only with EVPN over MPLS in the core. The EVPN E-Tree feature provides a way to categorize the interfaces as either “root” or “leaf” in a routing instance. In an EVPN E-Tree service, each Customer Edge devices attached the service is either a root or a leaf. The EVPN E-Tree service adheres to the following forwarding rules:

• A leaf can send or receive traffic only from a root.

• A root can send traffic to another root or any of the leaves.

• A leaf or root can be connected to provider edge (PE) devices in singlehoming mode or multihoming mode.

The EVPN ETREE service has all the benefits of EVPN such as active-active multihoming and load balancing loop detection for E-Tree.

In an EVPN ETREE service, the forwarding rule depends on the traffic source and destination for known unicast traffic or unknown unicast, broadcast, and multicast (BUM) traffic. Table 1 shows the forwarding rules within the ETREE service.

Note:

We don't support IGMP snooping, MLD snooping, or PIM snooping multicast optimizations with EVPN-ETREE.

Table 1: EVPN-ETREE Forwarding Rule Based on Traffic Source and Destination

Type of Traffic	Allowed/Not-Allowed	Filtering Location
Known Unicast Traffic from Root to Root	Allowed
Known Unicast Traffic from Root to Leaf	Allowed
BUM Traffic from Root to Root	Allowed
BUM Traffic from Root to Leaf	Allowed
Known Unicast Traffic from Leaf to Leaf	Not Allowed	At the ingress Packet Forwarding Engine
Known Unicast Traffic from Leaf to Root	Allowed
BUM Traffic from Leaf to Leaf	Not Allowed	At the Egress Packet Forwarding Engine
BUM Traffic from Leaf to Root	Allowed

If you do not configure a role for an interface, it will be assigned the role of “root” by default. All leaf interfaces are assigned a new mesh group with no local switching set to TRUE. This enables the ingress filtering for unicast traffic and all the leaf-to-leaf traffic will get dropped at ingress leaf interface. For BUM traffic, the filtering will happen at the egress Provider Edge based on the root/leaf label being carried in the packet.