downtime for migration from MPLS to VPN with BGP with bgp routing

[Carracido]

Hello community!

I have currently two sites connected through MPLS and I plan to configure a VPN with bgp routing to migrate traffic.

I am calculating the downtime that may require the migration from MPLS with static routing to the VPN with bgp routing.

I´m considering the following:

- Routes learned from IBGP has default AD = 200 and static route has default AD = 10
- After configuring BGP to route traffic over the VPN I should have the routes learned from BGP installed on the RIB but not on the FIB because the static route AD is lower
- To make the firewall placing the BGP routes into the FIB I will give the AD of the static route a bigger value than the bgp route. 
- After the switch between static-dynamic routing to bring the traffic into the VPN I´m gonna clear all the existing sessions to avoid performance issues.

I think the effective downtime could be not even 5 minutes. What do you think?

Thank you in advance!

[SutareMayur]

@Carracido

If you are all good with configuration then yes there should be minimal downtime. But as a best practice, you should have Maintenance Window of an hour or two. This is just in case of disaster situation.

Mayur