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Introduction to VXLAN MP-BGP EVPN Route Types

July 05, 2024 ,

Introduction to VXLAN MP-BGP EVPN Route Types

Before we start with the route types lets talk about the EVPN, EVPN (Ethernet  Virtual Private Network), enables  virtualized Ethernet communication between various network devices. Data center and service provider networks frequently employ EVPN to offer effective and scalable network connection.

EVPN provides several benefits over traditional Layer 2  VPN technologies, such as  Virtual Private LAN Service (VPLS). One of the main benefits of EVPN is that it enables multi-tenancy, where multiple customers or tenants can share the same physical infrastructure while maintaining separate and secure virtual networks.

While VXLAN is designed to provide the same Ethernet Level 2 services as VLAN, but with greater extensibility and flexibility. In a large multitenant environment, VXLAN provides a flexible, multitenant solution over a shared physical infrastructure. It operates by using IP plus UDP to travel over the physical network.

Introduction to VXLAN MP-BGP EVPN Route Types
Fig 1.1- VXLAN EVPN Basic Topology

EVPN Route Type 

The EVPN control plane advertises the following types of information:

  • Ethernet auto-discovery (AD) routes are route type 1. The Ethernet segment identity, Ethernet Tag ID, and EVPN instance information are advertised using this sort of Ethernet Auto-Discovery (EAD) route. Every Ethernet segment or every EVPN instance may receive EAD route ads.
  • Route type 2, or the advertisement route for MAC/IP: This broadcasts the MAC and IP addresses of the endpoints, or VTEPs, as well as endpoint reachability data.
  • The inclusive multicast Ethernet tag route, or route type 3, announces its desire to employ ingress replication for particular VNIs and is capable of performing multicast router advertisement.
  • Ethernet segment routes, or route type 4, are used to broadcast the length of the IP address, the originating router's IP address, and the Ethernet segment identifier.
  • Route type 5 is an IP prefix route that is used to advertise externally learnt routes and internal IP subnets to VXLAN networks.

The most focused route types are Route Type 2 and Route Type 3 and let's focus on those for a moment. 

Route Type 2:

As we discuss that the purpose of EVPN Route Type 2 is to broadcast MAC addresses and optional IP address information across a network. It is essential to EVPN instances because it makes it possible to build a redundant, effective Layer 2 network that spans a large geographic area. EVPN Route Type 2 minimizes broadcast traffic, which typically overloads network resources, and improves route targeting by mapping MAC addresses to IP addresses and matching Ethernet segments.

In order to maximize network service delivery and dependability, EVPN Route Type 2 makes use of a number of essential components. These consist of Labels for traffic segregation, Ethernet Tag ID, MAC Address Length, MAC Address, and IP Address Length. To guarantee that data packets take the most effective route through the network, each component makes a fine-grained contribution to the identification, routing, and segregation of traffic.

Route Type 3:

Broadcast, Unknown Unicast, and Multicast (BUM) traffic delivery via EVPN networks requires Type 3 routes. P-tunnels that should be utilized to send BUM traffic are discussed in Type 3 messages.

An EVPN instance's other PE devices would not be able to receive BUM traffic from the ingress router if Type 3 messages were absent. According to RFC 6514, a Provider Multicast Service Interface (PMSI) Tunnel attribute must also be carried by a Type 3 route.

The following Tunnel Types are defined, although your vendor might only support a subset of  tunnel types: