NAT object in LC

I'd recommend creating an iRule to SNAT your traffic on the way out so you can make sure it uses the proper link...

I'd do something like this:

1. Create a gateway pool with that specific link called "gw_pool_x" where x is your link

2. Create a SNAT Pool with the NAT address from that link - let's call it "snatpool_x"

3. Create an iRule and apply it to the VS.

when CLIENT_ACCEPTED {
  if {[[IP::client_addr] equals x.x.x.x] } {
     pool gw_pool_x 
     snatpool snatpool_x  } }

Something like that should work...