Migrating to other ISP/network

[chrisci]

Hello,

Sorry if similar questions has been asked already.

I have 100D with 5.4 firmware, 1 wan and 3 lans used ATM. In a few weeks I need to change ISP, what means I need to change all public IPs on the LAN side, as well as connecting IP on the wan. I have ~30 services behind the unit, mostly web pages. Some of those services should have the lowest downtime possible.

Is there any cookbook/paper/workflow which would help to plan what to do, in what order?

I can have isp1 active on wan1 and isp2 active on wan2, but I'm not sure how to route the traffic so my "old wan ips" would be accessible together with my "new wan ips".

I would prefer some solution which would allow gradual move, not burn the midnight oil and hope for the best.

Any input appreciated,

Chris