| Description | This article describes the behavior of the dynamic BGP session between 2 spokes for SDWAN/ADVPN 2.0. |
| Scope | Available from FortiOS 7.4.2. |
| Solution |
Starting from FortiOS 7.4.2, SD-WAN/ADVPN 2.0 can establish a dynamic BGP session over a shortcut. This is available for BGP on Loopback ADVPN design and no longer requires the BGP route reflection being configured in the Hub. Consider a typical network where 2 spokes have 2 uplinks to the Hub.
Once the first shortcut is established, the BGP session will run between both loopback addresses over this shortcut as shown below:
Should this shortcut come out of SLA, a new shortcut will be established, bypassing the out-of-SLA link.
User traffic will move over this new shortcut, but the dynamic BGP session will stay on the initial shortcut. Should the link stay out of SLA for a time greater than the shortcut idle expire timer, the initial shortcut will be flushed and the dynamic BGP session will move to the new shortcut. |
