Arista – BGP EVPN virtual L4-L7 service insertion.

In this blog I am going to show you how to provide L4-L7 service insertion within BGP EVPN fabric especially using eBGP between appliance and leaf pair switches. The challenge with L4-L7 service insertion is that such appliance can be deployed as virtual machine and could be easily migrated (vMotion) at any point across different ESX hosts connected to different leaf switches. That’s often seen in multi tenant environments where end customers are not big enough and they don’t need powerful physical appliance to provide L4-L7 service. If this is a case and there is a business requirement to engaged dynamic routing protocol between fabric and appliance, you must be sure that after migration of the appliance it can re-establish adjacency fast enough to minimize business impact.

Below is a network diagram which I am going to use to show configuration steps and some design consideration to achieve end-to-end connectivity for such design requirements.

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In this post I will go through the BGP EVPN + VXLAN for Data Center Interconnect with Arista switches. VXLAN provides the ability to decouple and abstract the logical topology by using MAC in IP encapsulation, from the physical underlay network. The VXLAN is describes in the RFC 7348 where you can read more about this technology. The initial VXLAN standard describe a multicast flood-and -learn for the overlay broadcast, unknown unicast and multicast traffic. Such flooding introduces some scalability concerns and to overcome the limitation of the flood-and-learn VXLAN the BGP EVPN can be used as the control-plane for VXLAN. The BGP EVPN has been define as the standard control-plane in the RFC 7432 for VXLAN overlays. The MP-BGP EVPN control-plane provides VTEP peer discovery and end-host reachability information across the fabric. In addition MP-BGP EVPN inherits multitenancy supports with VRF construct.

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