Your ISP should give you a single IP for your router WAN interface and than route the /29 subnet towards your WAN IP. With this you can have your /29 subnet inside your Router and do what ever you want with it, even route it further down.
my isp give me a /29 subnet,,x.x.x.72/29 (x.x.x.72-x.x.x.79), and x.x.x.78 is the gateway, x.x.x.72 and x.x.x.79 are not usable,, all packets to my subnet will route to my gateway, the problem is how can i use router os to route those packet(like, to x.x.x73-x.x.x.77) down to my computer behind the router os..
right now, i'm using cisco 478, cisco 478 connect to a switch, all my computer connect to the same switch, and manually setup the public ip for each computer, and works.
this is how i set up cisco 478
cbos# set nvram erase
cbos# set ppp wan0-0 ipcp 0.0.0.0
cbos# set ppp wan0-0 dns 0.0.0.0
cbos# set ppp wan0-0 login [username]
cbos# set ppp wan0-0 password [password]
cbos# set int wan0-0 disable
cbos# set int wan0-0 vpi 0 vci 32
cbos# set int wan0-0 enable
cbos# set int eth0 address xxx.xxx.xxx.78
cbos# set int eth0 netmask 255.255.255.248
cbos# set dhcp server disabled
cbos# set nat disabled