Verified answer

It sounds like you are entering a network address where you should have an IP address. For a 172.xxx.xxx.0/30 network the .0 is the network address, .3 is broadcast address and .1 and .2 are the usable IP addresses. So try 172.xxx.xxx.1/30 or 172.xxx.xxx.1/255.255.255.252

A couple things.

1.) if you're trying to change you IP address, i don't believe you can do it through the router.

2.) If you're trying to change the router address. I don't think you can do that either.

3.) If you can change the IP that way, and you're doing it to your computer. It must start with the 3 same numbers as the router.

for example, my router starts with 192.xxx.x.xxx

and all the computers in my house have an IP of 192.xxx.x.xxx

It would depend on what the 2nd and 3rd octets are. 172.16.0.0 -172.31.255.255 is a PRIVATE IP range, and would not be routable. It would also require a class B mask. /30 is an invalid mask for that range. A /30 mask only allows 2 usable addresses and is not valid for that IP range

Bad Mask

I hope you are not entering the actual xxx as you show? Also there should NOT be a /30 subnet. I think you need to study tcp/ip seriously before you mess with this.

if its an IP address it shouldn't have the /30 at the end.... are you referring to port 30?