- 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 Configuration
- Ethernet Segments
When a customer site is connected to one
or more Provider Edge (PE) routers via a set of Ethernet links, this set of links
constitutes an Ethernet segment (ES).
- Unique Identifiers Assignment for Ethernet
Segment LAGs
For multihomed BGP EVPN sites, Ethernet
segments need a unique 10-byte identifier called the Ethernet Segment Identifier
(ESI).
- Ethernet Segment Configuration and
Management
Ethernet Segments (ES) local to a device
are configured through the command line interface (CLI) and stored in the ES Manager
(ES-Mgr) module. The ES-Mgr handles multihoming configuration information, including
an ES
identified by a unique ID, the ES Type, associated Link Aggregation Group (LAG)
ID, and the
redundancy mode.
- Ethernet Segment Redundancy Mode
Ethernet Segments (ES) can be configured
to operate in all-active or single-active mode for a Layer 2 Virtual Private Network
(L2VPN)
using Ethernet Virtual Private Network (EVPN).
- Configuring an Ethernet Segment
Ethernet Segment (ES) type, redundancy
mode, and a LAG type can be configured for an ES for a Layer 2 Virtual Private Network
(L2VPN) using Ethernet Virtual Private Network (EVPN).
- Aliasing and Backup Paths
- Fast Convergence and Mass Withdrawal
When a link failure occurs between a
Customer Edge (CE) device and a Provider Edge (PE) device, all remote PE devices
are
notified through a BGP (Border Gateway Protocol) withdrawal message of a single
Ethernet
Virtual Private Network (EVPN) route.
- Designated Forwarder
- Split Horizon
In a multihomed network with a set of
Provider Edge (PE) devices on an all-active Ethernet Segment (ES), when a Customer
Edge (CE)
device sends Broadcast, Unknown Unicast, and Multicast (BUM) packets to a non-Designated
Forwarder (non-DF) PE, that non-DF PE forwards the packet to all other PEs in the
Ethernet
Virtual Private Network (EVI), including the Designated Forwarder (DF) PE for that
ES.
- Local Bias
Local bias involves replicating
multi-destination traffic received from the access side to all directly attached
Ethernet
Segments (ESs), regardless of the Designated Forwarder (DF) election state.
- Protocol Extension
In Protocol Extension encapsulation, the
ingress Provider Edge (PE) device can use the Broadcast, Unknown Unicast, and Multicast
(BUM) bit to indicate that BUM traffic has been replicated at the ingress.
- Ethernet Segment Routes (Type 4)
In a Border Gateway Protocol (BGP)
Ethernet Virtual Private Network (EVPN) multi-homing environment, Type 4 routes,
or Ethernet
Segment routes (ESRs), are crucial for the Designated Forwarder (DF) Election process,
ensuring efficient data delivery.
- Ethernet Auto Discovery Route (Type 1)
Ethernet Auto-Discovery (EAD) Routes are
essential for simplifying network configurations and ensuring stable connectivity
within
Border Gateway Protocol (BGP) Ethernet Virtual Private Network (EVPN) multi-homing
architectures. They facilitate the identification and association of Ethernet Segments
(ESs), making network management more intuitive.
- Advertising and Learning Multihomed MAC
Addresses and Snooped ARP Entries
Multihomed Media Access Control (MAC) and
MAC/IP refers to a local MAC address or a snooped Address Resolution Protocol (ARP)
entry
that has been learned over a local Ethernet Segment (ES). In singlehomed (SH) scenarios,
locally learned MAC entries are advertised by Route Type-2 (RT-2). Upon processing
the
route, the receiver learns about the egress Virtual Tunnel Endpoint (VTEP) for the
MAC, but
it does not have information about the egress port on the egress VTEP.
- BGP EVPN Multihoming Configuration
Example
The following illustration shows a
typical BGP EVPN multihoming configuration for a Customer Edge (CE) device with
the
multi-homed nodes VXLAN Tunnel Endpoint (VTEP) 1 and VTEP 2 of an Ethernet Segment
(ES).
- Configuring BGP EVPN Multihoming for a CE
Device
- Displaying BGP EVPN Multihoming
Information
You can use various
show commands to view information
about BGP EVPN multihoming.