DNS load balancing between ISP's

Hey!

Since the BIG-IP DNS GSLB function works on an Wide IP basis, I'd say it'd be best to move each DNS record at a time, creating a Wide IP for each FQDN. Then create two pools, one for ISP1 IP address and one for ISP2 IP address.

If you want one ISP to be the primary, you can use the Global Availability load balancing algorithm. That way the pool highest in the list will primarily receive traffic. But if that pool goes down, the secondary will be the one being sent back in the DNS response.

You can read more about GSLB here:

Manual Chapter: About Global Server Load Balancing

I hope this helps!

Let me know if you have any further questions :)