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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.

Figure 1: EVPN E-TREE Service
 EVPN E-TREE Service

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

In an EVPN ETREE service, the forwarding rule depends on the traffic source and destination. Table 1 shows the forwarding rules within the ETREE service.

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.

NSR and Unified ISSU Support for EVPN-ETREE

Nonstop active routing (NSR) and graceful Routing Engine switchover (GRES) minimize traffic loss when there is a Routing Engine switchover. When a Routing Engine fails, NSR and GRES enable a routing platform with redundant Routing Engines to switch over from a primary Routing Engine to a backup Routing Engine and continue forwarding packets. Unified in-service software upgrade (ISSU) allows you to upgrade your Junos OS software on your MX Series router with no disruption on the control plane and with minimal disruption of traffic. Both GRES and NSR must be enabled to use unified ISSU.

To enable GRES, include the graceful-switchover statement at the [edit chassis redundancy] hierarchy level.

Junos OS mirrors essential data when NSR is enabled. For EVPN ETREE, the local EVPN ETREE leaf label that is advertised to other PE as part of the ETREE extended community will be mirrored on the standby Routing Engine. For information on other mirrored data and NSR data flow, see NSR and Unified ISSU Support for EVPN .

To enable NSR, include the nonstop-routing statement at the [edit routing-options] hierarchy level and the commit synchronize statement at the [edit system] hierarchy level.