We have a redundancy connection with our ISP from two different sites BG1 (border gateway working), and BG2 (border gateway standby), the ISP use local preference in order to select the path and the Borders gateways use RANK (in both sites) in order to send the traffic to the ISP. Our two Border gatewas are connected through MPLS backbone using bgp between PE-CE, and the routing protocol between border gateway and CE is ospf.
The problem happened when the interface between BG1 and ISP goes down, BG1 send LSA update to the CE (1500 routes) in order to inform to ospf that the link is down (expected behavior), so all of the traffic is redirected to BG2, but after 60 seconds BG1 will send to CE1 new LSAs update (400 routes) even the interface is down, so the CE1 will try to send all those routes through BG1 but due to the interface is down those networks are not reachable.
Please guys can you help us to understand which timers or parameters are causing this abnormal behavior??.
Thanks any comment is very welcome