88.211.91.1 255.255.255.248
so the subnet is 88.211.91.0 /29
you have 88.211.91.1 through 88.211.91.6 available to use...
88.211.91.7 would be your broadcast address for that subnet
likely the .1 address is what your isp will be using as your gateway.. you can then set up static nat...