EVPN MPLS E-Tree Scenario 1
Overview
Ethernet VPN Ethernet-Tree (EVPN E-Tree), is a networking solution designed to manage communication within broadcast domains, incorporating redundancy through multi-homing in a network. It optimizes traffic routing and control, especially in scenarios where specific services or devices need controlled communication. It categorizes network nodes based on predefined definitions of EVPN Instances as Leaf or Root, allowing or restricting communication between them. OcNOS supports EVPN MPLS E-Tree based on Scenario 1 (SC-1) of RFC 8317, designating each Provider Edge (PE) node as either a Leaf or a Root site for Virtual Private Network (VPN) using VXLAN and MPLS EVPN.
Feature Characteristics
Scenario 1: Leaf or Root Site(s) per PE
Scenario 1 involves a topology with three PE nodes: PE-1, PE-2, and PE-3. PE-1 and PE-2 are Multi-Homed nodes (MH-1 and MH-2), with PE-3 acting as the Root node. PE-1 and PE-2 function as Leaf nodes and are part of a single home access interface (SH1 and SH2).
Figure 55. EVPN E-Tree
The classification ensures that communication follows specific rules:
| • | Communication between Leaf hosts is restricted, as indicated by red dotted lines with a cross mark (X) in the topology diagram. However, communication between Leaf and Root nodes, as well as between Root nodes, is permitted, marked by green dotted lines. |
| • | Leaf nodes within PE-1 and PE-2 are isolated from each other, preventing intra-PE communication. |
The scenario 1 is achieved through two main concepts:
| 1. | Inter-PE Communication |
| • | The inter-PE Route Target (RT) Constraint Method is applicable only to Single-Homing (SH) devices. Two RTs per broadcast domain are utilized, with Leaf PEs exporting Leaf RTs and Root nodes exporting Root RTs. Leaf nodes import only Root RTs, allowing communication with Root PEs while preventing communication with other Leaf nodes. RT constraints limit the import of specific EVPN routes (MAC-IP and IMET routes) to designated paths for inter-PE communication. |
| • | IPI employs a proprietary method to support inter-PE connectivity for both SH and MH devices, using BGP extended community to advertise Leaf Indication in BGP routes and influence traffic flow for both Unicast and BUM traffic. This method enables implementation of ARP or ND cache suppression and MAC mobility sub-features specified in RFC-7432. |
| 2. | Intra-PE communication: Local Split Horizon controls intra-PE communication between Attachment Circuits (ACs) within Leaf PE nodes, ensuring that traffic between ACs does not egress to other Leaf ACs. |
This functionality depends on hardware capabilities.
Benefits
EVPN E-Tree Scenario 1 offers benefits in networking environments by providing efficient traffic control, enhanced security, scalability, and improved performance.
Efficient Traffic Control: Controls traffic between Leaf and Root sites across PEs, ensuring only authorized communication flows.
Enhanced Security: Leaf-to-Leaf traffic is blocked and split-horizon prevents local Leaf-to-Leaf communication, reducing risk of unauthorized access.
Scalability: Supports multiple Leaf and Root sites across the network, scalable for small to large enterprise deployments, but each PE hosts either Leaf or Root.
Improved Performance: Optimizes forwarding and filtering paths within SC-1 deployment, ensuring efficient delivery of critical data.