ACI Multi-Site Connectivity to External Layer 3 domain

Multi-Site Connectivity to External Layer 3 domain

With the help of L3Out connection, communication between VRF instance defined in ACI to external network is done. There are two options design available for L3Out connectivity & its Configuration.

• L3Out Connections defined on border leaf nodes.
• EVPN-based L3Out Connection (GOLF design)

Let’s understand how these different Modes of L3out Connections works in ACI fabric.

L3Out Connection on border leaf nodes

There are two scenarios where L3out is supported in ACI infrastructure till now release, also as shown in below figure.

• L3Out design on dedicated pair of WAN Edge Routers
• L3Out design over Shared pair of WAN Edge Routers

Refer below figure for L3Out design on dedicated pair of WAN Edge Routers

Refer below figure for L3Out design on shared pair of WAN Edge Routers

In both cases and before ACI release 4.2(1), it was required to deploy dedicated L3out connection at each site, but after release 4.2(1), a new function named “Intersite L3Out” was introduced.

Below is the supported/ Not Supported design scenario prior to release 4.2(1).

Refer figure which shows supported design

Not Supported Design

In ACI multi-Site design, IPN network is used for all east and west endpoints communication traffic and L3Out Connection over WAN network is used to establish north to south connectivity to remote clients.