Hi guys, I write a proposal about implementing routing method for guest networks using VLAN isolation. At the moment, they can reach each other due to interVLAN routing in VPC model, but can not in Guest network model. So the key point is make some static routes between them, including iptables rules for filtering ports and protocols. Please take a look on my proposal, link below.
https://cwiki.apache.org/confluence/display/CLOUDSTACK/Routing+between+Guest+networks -- N.g.U.y.e.N.A.n.H.t.U
