Your outbound traffic needs to be NAT'ed in order for your internal traffic to be routeable on the internet--usually this is done by the cable modem, but in your case it appears to be acting as a pass-through bridge for the public IP being assigned from your ISP. You'll need to either 1. put a firewall (Juniper SRX for example) inline between the EX and the cable modem, or 2. put the cable modem into route mode instead of bridge mode, where it keeps the public IP on its external interface and you assign a small private subnet on the inside interface. In either case you'll also need to configure static routes for your internal subnets so that the cable modem or firewall knows that they exist.
