This is the setting I was planing on using
MX LAN IP 10.0.0.181
MX WAN - DHCP (HFC internet).
MX Port 4 , WAN-2 Static IP 10.0.0.179. gateway 10.0.0.180 which is LAN Interface for Cisco 1900+ router.
Cisco Router LAN IP g0/1 = 10.0.0.180.
Cell c0/0/0 -DHCP its will get public IP when connected.
And Im will set MX to only switch over the WAN-2 if WAN-1 is down.
Now for Forwarding rules I can set them in the Cisco router so if its on than any forward should work from Cisco without having MX block it.
IF you see any issue with this please let me know otherwise will post back tomorrow of resualt.