In the first part of this series, we talked about Edge mode and in the second part we talked about one-arm mode. In this installment, we will talk about the inline mode of deployment. Inline mode is commonly used on appliances that provide WAN-Optimization functionality.

Inline mode is commonly provided on WAN-Optimization devices. Just like PBR or one-arm mode, inline mode of deployment helps a customer start off with SD-WAN without the costly rip and replacement of existing devices.

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From an SD-WAN insertion perspective, one needs to re-cable connections between Switch-to-SD-WAN and Router-to-SD-WAN. Apart from this, one doesn’t need to change anything on the LAN devices: the default gateway still remains the Edge Router (or the layer-3 switch). SD-WAN device acts in a promiscuous mode in this mode, classifies the incoming LAN Application, and based on the Application requirements maps it to the best available link via the SD-WAN overlay.

Unlike PBR mode, there is no requirement to configure access-lists and PBR rules on the Edge device. So, if there are huge access-lists, this mode provides lower overhead. Again, just like PBR mode, if the SD-WAN device goes down, then it goes into a bypass mode wherein all traffic seamlessly passes through the SD-WAN device. A user doesn’t get SD-WAN treatment; however, traffic and applications are not impacted.

To conclude this three-part blog on the plethora of deployment choices,it is important to note that we provide High Availability options in all the three modes. I’ll cover High Availability options in a future post, but in the meantime, the table below summarizes the different modes and the pros and cons of each mode.

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