Can I reuse BGP settings when migrating Direct Connect VIF to a new physical connection?

When migrating from one Direct Connect connection to another within the same region, you cannot directly reuse the same BGP settings while both VIFs exist simultaneously. This is because VLAN IDs must be unique, and having identical BGP configurations on two active VIFs would create conflicts.

For your migration plan, you have two options:

1. Delete the old Transit VIF first, then create a new one with the same BGP settings on the new connection. This approach ensures no configuration conflicts but creates a period of downtime.

2. Follow a more gradual migration approach with these best practices:

• Create the new Transit VIF on the new connection with different VLAN ID but similar BGP configuration
• Verify you're receiving the same set of routes on both old and new VIFs on your on-premises router
• Test by advertising a small set of routes from on-premises on the new VIF to verify proper configuration
• Advertise the same on-premises prefixes on both VIFs, but configure your on-premises router to prefer the new VIF (using BGP attributes like Local Preference)
• Once traffic is flowing properly through the new connection, you can decommission the old VIF

Since you're using a Direct Connect Gateway attached to a Transit Gateway, the migration should be relatively straightforward as long as you follow these steps. The key is to ensure proper BGP configuration and routing preferences to maintain connectivity during the transition.

For minimal downtime, I recommend creating the new Transit VIF before disconnecting the old one, testing connectivity through the new path, and then performing the physical cutover. This approach allows you to validate the new configuration before making the physical switch.
Sources
Migrate an AWS Direct Connect virtual interface - AWS Direct Connect
Simplify global hybrid connectivity with AWS Cloud WAN and AWS Direct Connect integration | Networking & Content Delivery