How is BGP Configuration on Velocloud VPN

In Velocloud, how is BGP established between Edge?

To a branch I think that it is via VCG when branch office VPN,

but in that case do you need special one to establish EBGP?

In my environment, I can establish it with IBGP, but it can not be established when I change to EBGP.

I think there is a possibility that Peer can not be reached by 1 hop.