GTM sending data to VIP IP which is down.

How have you added the LTM VIP's (which is the VS is the GTM Pool) in the GTM Pool. Are you adding it as Generic host or under Iquery.

And when you said the VIP Is down on the LTM, is the GTM marking it as UP. The LTM VIP would have passed the tcp handshake from the GTM hence it would've marked it as UP. If you can post your GTM level configuration and the LTM VIP which is down. Can give you detailed solution.

But here's what I think you have, Your VIP2 is down and it has http profiles. But on the GTM pool, you have added the VS with basic tcp half open. So the GTM will mark it as UP. Because the tcp handshake gets successful to the VIP. Only when the next HTTP GET request is sent, the traffic would fail. So its not wrong the GTM marking it down. Hope it clarifies.