First, FYI the rpcallowip parameter is related to JSON-RPC API requests to a specific node, so it doesn't affect the peer-to-peer blockchain protocol.
The problem is almost definitely related to your firewall or VM configuration so it's hard for us to give a definitive answer. You need to have a different IP address set up for each VM instance, so that each can communicate with the other. If you've done this successfully, you should be able to use telnet to at least establish that one instance can talk to the other, on the right port.
For example the equivalent test for a node on the bitcoin network would be:
telnet seed.bitcoin.sipa.be 8333