SD-WAN site communicating with non SD-WAN site over eBGP
When a site without SD-WAN appliance is communicating with another site with SD-WAN appliance (Site-A) over a single WAN path (only internet is available), and if the site with SD-WAN appliance (Site-A) loses internet connectivity, then the site without SD-WAN can communicate with Site-A through another SD-WAN appliance site (Site-B). Site-B funnels traffic from the site without SD-WAN appliance to the Site-A.
Communication between SD-WAN sites using Virtual Path and eBGP
Provides underlay route learning to communicate with remote site local subnets when the virtual path is down between two sites while the Virtual WAN appliance is still up and running.