http://msdn.microsoft.com/en-us/library/windowsazure/jj156075.aspx
If you dont see your device listed as a supported device, your VPN device still might work with Windows Azure Virtual Network. However, the device will not be fully supported and no configuration scripts will be supplied. In order for a network device to work with Windows Azure Virtual Network, it must support the following:
VPN device must have a public facing IPv4 address
VPN device must support IKEv1
Establish IPsec Security Associations in Tunnel mode
VPN device must support NAT-T
VPN device must support AES 128-bit encryption function, SHA-1 hashing function, and Diffie-Hellman Perfect Forward Secrecy in "Group 2" mode
VPN device must fragment packets before encapsulating with the VPN headers