do you want to direct all traffic or just part of it ? I mean all destination or just a group ?
Do you learn these destination via BGP from this next hop ?
If not, can you enable iBGP between them ?
Where is the traffic sent right now ?
What you have to do is have your best route for each destination pointing to this internal device.
You can use static routes or an IGP like OSPF or iBGP.
The goal is to have a route pointing to this internal device and play with the metric to make this route the prefered one.
Hope this help,
Gilles.
