We currently have two ISPs for our internet connectivity and we are load sharing traffic between the two. Currently we have static routing with these ISPs. Our plan is to change that and implement BGP multihoming with the two ISPs. Also currently we have only one router which talks to both the ISP routers. We plan on implementing HSRP pair with this router and use them as WAN/Edge routers which will do BGP with the ISPs.
What is the best/right approach to do this? Since we will be migrating to BGP, we will get new IP space and we need some time to change the applications from current public ip space to new ip space. Should I implement HSRP pair first, do BGP with the ISPs and then migrate the applications to new ip space? Or is there a better approach? Can I have static routing and BGP peering with the ISP at the same time, until I migrate all the applications from current public ip space to new ip space?