Internet access doesnt work with LB as gateway and snat disabled but if we use a snatpool it works. Does anybody know why?

So a couple of things going on here that might be causing problems. 1. is the F5 the network gateway for the box that is trying to access the internet? If it's not, and you're not using snat, the F5 will be bypassed on the return (synack).. depending on your config, this could be the problem. 2. there could be rules restricting what addresses are permitted out to the internet. The snat addresses might be permitted, but the client address may not be. Again, depending on configuration.

But let's start with some really basic stuff.. 1. is the client addressed with a public address (ie, not 10.x.x.x or 192.168.x.x or etc) address? 2. is the snat address public? 3. is something else in the path that is doing filtering? 4. is there something else in the path doing address translation public to private? 5. is the f5 the default gateway for the client network?