Appendix

Feature History for Multihoming in a BGP EVPN VXLAN Fabric

This table provides release and related information for the features explained in this module.

These features are available in all the releases subsequent to the one they were introduced in, unless noted otherwise.

Release

Feature

Feature Information

Cisco IOS XE Bengaluru 17.16.1

Single-Active Mode

In single-active mode, only one Virtual Tunnel Endpoint (VTEP), among a group of VTEPs that are attached to the particular Ethernet segment, is allowed to forward traffic to and from that Ethernet segment.

Multihoming in single-active mode was introduced only in the form of dual-homing, allowing a CE device to be connected to two VTEPs.

Cisco IOS XE 17.18.2

All-Active Mode

In all-active mode, downstream devices can connect to multiple VTEPs simultaneously using a standard PortChannel interface.

Cisco IOS XE 17.18.2

Hierarchical BGP Sessions

With hierarchical BGP sessions, EVPN multihoming with fabric control planes enables scalable and resilient campus networks by replacing legacy STP architectures with VXLAN fabric cores.

Cisco IOS XE 17.18.2

Routed Overlay

Routed overlay is virtual network built on top of a physical infrastructure and it uses VXLAN to securely connect endpoints.
Cisco IOS XE 17.18.2

Overlay: Distributed Anycast Gateway Routed

Distributed Anycast Gateway (DAG) is an overlay architecture that allows multiple leaf switches or VTEPs to share the exact same default gateway IP and MAC address for a given subnet across the fabric.

Cisco IOS XE 17.18.2

Overlay: Distributed Anycast Gateway Routed

In DAG bridged overlay inter-subnet traffic between different bridge domains is routed centrally, while this traffic remains bridged natively across the fabric.

Use Cisco Feature Navigator to find information about platform and software image support. To access Cisco Feature Navigator, go to Cisco Feature Navigator.

Terms and Definitions

Terms and their definitions used in EVPN multihoming.

Term

Definition

Anycast IP gateway

A unified IPv4 or IPv6 gateway address for each IP subnet between one or multiple pairs of EVPN multihoming redundancy groups.

Anycast virtual MAC

A unified gateway link-layer MAC address for each IP subnet between one or multiple pairs of EVPN multihoming redundancy groups.

Broadcast, Unknown Unicast and Multicast (BUM)

BUM category network traffic (such as ARP/ND, miss-MAC, and Layer 2 multicast) over local Layer 2 ES trunk port or bridge across IP/VXLAN networks.

Designated Forwarder (DF)

The DF in a VTEP role auto elects the role to forward BUM traffic, preventing duplicates and loops in multihomed Layer 2 networks.

Ethernet Segment (ES)

An ES is a Layer 2 port in access or trunk mode, a part of the bundled links that connects to a directly attached Layer 2 network device.

ES Identifier

The ESI is a unique auto-generated or manually assigned 10-byte value for each ES port. The pair of VTEPs in the same redundancy group auto discovers and synchronizes Layer 2 ES ports to logically bind in a distributed EtherChannel group.

Redundancy Group (RG)

A pair of Catalyst 9000 series switches with a common ESI that supports a loop-free Layer 2 multipath resilient forwarding solution.

Ethernet Virtual Interface (EVI)

An Ethernet virtual network instance that binds each VLAN with a unique L2VNI identifier value that extends the Layer 2 bridge network over the IP routed network.

Ingress Replication (IR)

One-In-N-Out method extending BUM traffic from a local Layer 2 port over IP/VXLAN unicast to a remote targeted VTEP IP.

IP-VRF Route-Target (RT)

RTs are extended BGP community attributes used to control the import and export of IPv4 and IPv6 network prefixes within a logically segmented IP network.

MAC VRF

A virtualized and isolated MAC address forwarding table that supports secure extended Layer 2 bridge-domain for VXLAN enabled networks.

Multicast Replication

One-in-one-out method to extend the BUM traffic from a local Layer 2 port over IP/VXLAN to any remote VTEP registered in a common multicast group.

Non-Designated Forwarder (non-DF)

A VTEP not designated to forward BUM traffic to local VLAN/ES interfaces to prevent Layer 2 loops. The unicast/multicast traffic continues to be forwarded based on Layer 2 or Layer 3 tables.

Network Virtualization Endpoint (NVE)

A system-wide single logical interface that binds all Layer 2 and Layer 3 overlay networks, and supports to encapsulate outgoing and de-encapsulate incoming VXLAN traffic over an IP network.

MAC-VRF Route-Target (RT)

RTs are extended BGP community attributes used to control the import and export of MAC, MAC/IPv4 and MAC/IPv6 individual host prefixes within a logically extended Layer 2 network.

System MAC

MAC address ranges from the system internal pool to use for LACP system ID and other purposes.

Layer 2 Virtual Network Identifier (L2VNI)

A 24-bit value in VXLAN header that assists in maintaining segmentation and extension of local VLAN or bridge-domain between VTEPs.

Layer 3 Virtual Network Identifier (L3VNI)

A 24-bit value in VXLAN header that assists in maintaining IPv4/IPv6 routed data communication within each virtualized IP routing space between VTEPs.

Virtual Extensible Local Area Network (VXLAN)

An overlay networking technology converging routing and bridge networks over IP core networks.

EVPN Multihoming BGP Route Types

BGP EVPN multihoming supports multiple route types that collectively provide control plane intelligence for both traditional non-fabric and fabric networks. The BGP control plane between targeted ES systems enables scalable, loop-free, all-active Layer 2 redundancy across multiple provider edge devices. BGP EVPN multihoming also supports fast convergence during unplanned link or node failures, delivering deterministic non-stop business communication within the enterprise campus networks.

Table 1. BGP route types

Route type

Description

1

Used for network-wide messaging, primarily in multihoming scenarios. It advertises the Ethernet Segment Identifier (ESI) to enable functions like split-horizon filtering, aliasing (load balancing), and fast convergence/mass MAC withdrawal in case of a link failure.

Used for network-wide messaging, primarily in multihoming scenarios. It advertises the Ethernet Segment Identifier (ESI) to enable functions like split-horizon filtering, aliasing (load balancing), and fast convergence/mass MAC withdrawal in case of a link failure.

  • EAD-Per-ES: split-horizon filtering, fast convergence/mass MAC withdrawal

    EAD-Per-EVI: aliasing. It can be achieved using the MAC IP proxy route and can be suppressed through the configuration.

2

MAC-only: can be suppressed through the configuration to reduce route scale.

MAC-IPv4: Advertises endpoint reachability information, including both the MAC and IPv4 addresses of hosts connected to the network. It provides MAC/IP address bindings which allow for ARP suppression, reducing broadcast traffic in the network.

MAC-IPv6: Same for IPv6 hosts reachability.

3

IMET: Used to set up the flooding tree for Broadcast, Unknown Unicast, and Multicast (BUM) traffic for a specific virtual network interface (VNI). It announces the source's capability and intention to use ingress replication for BUM traffic.

4

ES: Advertises the ESI and the originating router's IP address. This route is critical for the auto-discovery of multihomed Ethernet segments and the Designated Forwarder (DF) election process, which prevents duplicate BUM traffic from being sent to multihomed devices.

5

IP-Prefix: Advertises internal IP subnets and externally learned routes, typically for inter-subnet forwarding (Layer 3 routing). These routes are essential for efficient routing between different VLANs/subnets within the VXLAN fabric.

6

SMET/IGMP-MLD Proxy: Used to distribute the explicit interest of a host or virtual machine in receiving traffic for a specific multicast group (either [*,G] or [S,G]). This allows Ethernet segment switches to build a more selective forwarding list for multicast flows, avoiding unnecessary flooding.

7

IGMP/MLD Join Sync: Used in multihoming scenarios to synchronize the Internet Group Management Protocol (IGMP) or Multicast Listener Discovery (MLD) join states between a pair of Ethernet segment switches connected to the same Ethernet Segment Identifier (ESI). This ensures that if the designated forwarder fails, the backup ES switch has the correct multicast state to take over seamlessly.

8

IGMP/MLD Leave Sync: Functions similar to Type 7, but for synchronizing IGMP or MLD leave messages. This ensures that a pair of multihomed Ethernet segment switches are aware when a receiver is no longer interested in a multicast stream, allowing for efficient pruning of the multicast forwarding tree.