EVPN FAQ

What is EVPN?

Ethernet VPN (EVPN) is a new technology that is used to extend Ethernet circuits across Data Center and Service Provider networks. It is expected to succeed other L2VPN transport methods such as BGP-based L2VPN (RFC6624), LDP-Based L2VPN (RFC4906) and VPLS.

EVPN introduces a set of new features that were not available in L2VPN and VPLS environments, most noticeable of which are All-Active Multi-homing across multiple PE devices and more efficient handling of L2 Multicast traffic.

Refer to RFC 7209 to better understand the rationale for creating EVPN.
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EVPN MPLS Port-Based VLAN-Aware Bundle Service

In this article, we will review EVPN MPLS Port-Based VLAN-Aware Bundle Service  configuration example using Juniper MX devices. As per Port-Based VLAN-Aware service definition in RFC7432, all of the VLANs on the port are part of the same service and are mapped to a single bundle without any VID translation.

EVPN VLAN-Aware Bundle Service
EVPN VLAN-Aware Bundle Service

In our sample, we will add L3 IRB interfaces to VLANs, simulating L3 Default Gateways.
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EVPN MPLS Service Types Illustrated

EVPN VLAN-Based Service

With this service interface, an EVPN instance consists of only a single broadcast domain (e.g., a single VLAN).  Therefore, there is a one-to-one mapping between a VID on this interface and a MAC-VRF. Since a MAC-VRF corresponds to a single VLAN, it consists of a single bridge table corresponding to that VLAN.

EVPN VLAN-Based Service
EVPN VLAN-Based Service

Click here for Juniper MX Configuration Example.

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EVPN MPLS Service Types

Broadcast Domains

(VLANs)

Bridge Table MAC VLAN to MAC-VRF Mapping Ethernet TAG ID VID Translation
VLAN-Based Service Single Single Can overlap between VLANs one-to-one 0 Egress PE
VLAN Bundle Service Multiple Single Unique for all VLANs many-to-one 0 Not Supported
Port-Based Service Multiple Single Unique for all VLAN many-to-one 0 Not Supported
VLAN-Aware Bundle Service Multiple One per VLAN Can overlap between VLANs many-to-one VID or normalized TAG ID

 

Supported
Port-Based VLAN-Aware Service Multiple One per VLAN Can overlap between VLANs many-to-one VID

 

Not Supported

For more information on EVPN, please refer to our other articles on this topic:

http://www.bgphelp.com/tag/evpn/

EVPN Type 2 (MAC/IP Advertisement route) Explained

Type 2 routes are used to advertise MAC addresses and IP addresses that might be associated with aforementioned MAC addresses.

In order to advertise Type 2 routes, PE needs to learn MAC addresses from the directly attached CEs. This is done via normal data-plane learning mechanisms. RFC 7432 also allows for MAC address learning via control plane interaction between PE and CE, although we have not see this implemented by any vendors.

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EVPN Type 1 (Ethernet Auto-Discovery) Explained

Type 1 advertisements are used for two distinct functions – Fast Convergence and Aliasing. EVPN Fast Convergence allows PE devices to change the next-hop adjacencies for all MAC addresses associated with a particular Ethernet Segment. EVPN aliasing allows traffic to be balanced across multiple egress points.

Type 1 routes are only advertised if Ethernet Segment Identifier is set to non-zero value, meaning that Type 1 routes are only originate for multi-homed sites.

Please refer to the following cheatsheet if you are not familiar with EVPN Terminology.

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EVPN Terminology Reference (RFC 7432, etc)

  • AC, A-C: Attachment Circuit
  • AD, A-D: Ethernet Auto-Discovery route
  • Ethernet Segment (ES): When a customer site (device or network) is connected to one or more PEs via a set of Ethernet links, then that set of links is referred to as an ‘Ethernet segment’.
  • Ethernet Segment Identifier (ESI): A unique non-zero identifier that identifies an Ethernet segment is called an ‘Ethernet Segment Identifier’. ESI 0 denotes a single-homed site.  ESI {0xFF} (repeated 10 times) is known as MAX-ESI.
  • Ethernet Tag: An Ethernet tag identifies a particular broadcast domain, e.g., a VLAN. An EVPN instance consists of one or more broadcast domains.
  • Ethernet Tag ID: 32-bit field containing either a 12-bit or 24-bit identifier that identifies a particular broadcast domain (e.g., a VLAN) in an EVPN instance.
  • EVI: An EVPN Instance spanning the Provider Edge (PE) devices participating in that EVPN.
  • EVPN: Ethernet Virtual Private Network.
  • IPL: IP address length
  • IRB: Integrated Routing and Bridging interface
  • NVE: Network Virtualization Edge
  • MAC-VRF: A Virtual Routing and Forwarding table for Media Access Control (MAC) addresses on a PE.
  • MAX-ET: Reserved Ethernet Tag ID {0xFFFFFFFF} is known as MAX-ET
  • MAX-ESI: Reserved ESI {0xFFFFFFFFFFFFFFFFFFFF} is known as MAX-ESI
  • ML: MAC address length
  • TS: Tenant System
  • VA: Virtual Appliance