specifying the default gateway to some dummy ip address (same subnet) in both virtual machines. 

$ vi /etc/defaultrouter and add the IPADDRESS of your router. 

EXAMPLE: 

vi /etc/defaultrouter 
192.168.157.100
 
reboot to test. or netstat -r  (This will show the current routing table) 
 
Another Example: route add destination gateway 
Example:

# route add default 192.168.157.100 
 
netstat –r (This will now show your 'new' default gateway).