BGP EVPN Multihoming Overview

BGP EVPN multihoming enhances redundancy for BGP EVPN by providing multiple, distinct Provider Edge (PE) connections (uplinks) for Customer Edge (CE) devices. This multi-attachment capability offers redundant, all-active connectivity to the EVPN core network and extends this redundancy across the entire network connected to the core.

BGP EVPN multihoming addresses common challenges associated with all-active redundancy, such as duplication and looping of Broadcast, Unknown unicast, and Multicast (BUM) traffic.

Note: The RUCKUS implementation of BGP EVPN Multihoming supports a maximum of two homes (uplinks), which is why it is also called Dual Homing.
SZ can add conditions as necessary. This list is good for FI

Important Terminology for BGP EVPN Multihoming

The following are common terms used in reference to BGP EVPN Multihoming:

  • BUM: Broadcast, Unknown unicast, and Multicast
  • CE: Customer Edge
  • DF: Designated Forwarder
  • ES: Ethernet Segment
  • EVPN: Ethernet Virtual Private Network. A common implementation is Ethernet over VXLAN. This is the implementation outlined in this chapter.
  • EVI: Ethernet Virtual Instance
  • LAG: Link Aggregation Group
  • MAC: Media Access Control
  • PE: Provider Edge
  • RD: Route Distinguisher
  • SH: Split Horizon
  • VE: Virtual Entity. A set of virtualized network resources or devices that are connected to multiple uplinks or network paths.
  • VNI: Virtual Network Identifier
  • VTEP: Virtual Tunnel End Point. In BGP EVPN terms, a VTEP can also be referred to as a leaf.
  • VXLAN: Virtual eXtensible Local Area Network

Multiple modules in the system are involved in the implementation of BGP EVPN. These are described in subsequent sections.

Ethernet Segment Redundancy Mode

Ethernet Segments (ESs) can be configured to operate in all-active or single-active mode. When all-active mode is configured for an ES, the ES is simultaneously up on all the member VTEPs of the ES. Traffic is distributed across all VTEPs, providing load balancing and redundancy.

In Single-active mode, only one ES member is active, while the others are set to DOWN. If the ES goes down on the currently active VTEP, another VTEP becomes active and brings the ES member port back to an operational status of UP.

Ethernet Segment Identifier

The Ethernet Segment Identifier (ESI) is a 10-byte identifier used to uniquely identify an Ethernet segment within the BGP EVPN fabric. There are three different types of ESIs, depending on how they are derived.

  • Type 0: With this type, the first byte is automatically 00 (denoting Type 0) and you manually configure and manage an arbitrary 9-byte ESI value. It offers you the flexibility to define the ESI value without any specific format constraints, making it suitable for various custom configurations.
  • Type 1: Use this type when employing LACP between the PE and CE devices. The ESI value is automatically generated by automatically setting the first byte to 01 (denoting Type 1), combining the CE LACP System MAC address (6 bytes) and the CE LACP Port Key (2 bytes), with the remaining byte set to zero. This automation simplifies your configuration process by deriving the ESI value directly from LACP parameters.
  • Type 3: This type involves automatically setting the first byte to 03 (denoting Type 3), and your configuring a MAC-based ESI value by combining the System MAC address (6 bytes), which must be identical across all multi-homed PEs, and a Local Discriminator value (3 bytes).

Parent topic: BGP EVPN