Ip address issue

what's wrong with IP address 192.168.88.49 when subnet mask is 255.255.255.0 and default gateway is 192.168.1.15

Your default gateway is not on the same IP network as the host address. With that subnet mask your default gateway will need to be 192.168.88.x. Or, if the default gateway device's address cannot be changed, you could change the address of the PC instead to 192.168.1.x

I would go through the reviews they have here on subnetting and supernetting.

basically that is a class C network meaning that the first three numbers (192.168.88.) is your netowork the last is your computer's number number on the network. (like a normal address the first numbers are the street, the last number is the street number) the whole purpose of a gateway is to get you to another network. So right now your gateway is on a different network then your computer.

(in my example your gateway is on elm street and your computer is on peak st with no ways out, because the .88.x network has no "Gateway" to bridge the gap to the new network)

I hope that helps...