I have a /29 subnet assigned by my ISP, with an SonicWALL office router and a Cisco voice router hooked up to a 'net-rail' of sorts with untagged VLAN switch ports connecting my ISP router's output and the two firewalls.
I'd like to use this as a routed subnet so that all connections hit my office firewall and I can DNAT to our internal network.
Is there anything that can be done without significant changes on our ISPs router?