It is not a correct design. Well you can use the other ips in that range, only if it falls in a different segment.
In this scenario 192.168.1.253 falls in the range of 192.168.1.0/24.
Hence you cannot an ip which falls in the subnet somewhere else. It is not Proper design.
if you use 192.168.1.253/30 & 192.168.1.254/30 you can use 192.168.1.0. if it is /30. if it is 192.168.1.0/24 , ip address 192.168.1.1/24 can reach 192.168.1.253 & 192.168.1.254. but tell me whether you wanted to keep 192.168.1.0/24 on the LAN interface & 192.168.1.253 & 254/30 in WAN interface?
basically the 192.168.1.0 network points somewhere else, the wan links are in a seperate place, doesnt 192.168.1.253 and 254 fall within the 192.168.1.0/24 network though, my question really is, can I still use the whole /24 range ?
to make you more simple to understand, 192.168.1.0/24 pc's cannot ping 192.168.1.253/30 & 192.168.1.254/30. as it is considered as different network.
thanks for that, so with them both being different networks, I can use more /30's in from the 192.168.1.0 network, and yet still use the whole /24 of that network ?
You can, as long as 'ip classless' is enabled on your router _and_ /30 networks are advertised by some classless routing protocol (RIPv2, OSPF, EIGRP, but not classfull RIPv1 or IGRP) _and_ they're not summarized. Sometimes such situation is result of (auto)aggregation with discontigous subnets, will work but not necessarily a good thing and I'd try to avoid this whenever possible.