A subnet mask of /28 would be 255.255.255.240, not 248, not 248. Having 32 subnets with 8 hosts per subnet is impossible with the given mask. The purpose of the mask is that is shows which bits within a network can and can't change. 240 in binary = 1111 0000. This means the first 4 msb in the last value cannot change AND be in the same network.
A Full IP subnet cheat sheet in a table format for your day to day subnetting tasks. IPv4 chart includes cidr, subnet mask, wildcard and IPv6 chart includes number of /48, /56, /64, /127 per prefix Understanding subnet mask, a fundamental component of IP Since the ‘1’ bits need to be contiguous, the octets of the subnet mask can only have the following values: 128, 192, 224, 240, 248, 252, 254, 255. As shown in the table, the shortest subnet mask has a length of /8 (corresponding to 255.0.0.0) while the longest has a length of /32 (corresponding to 255.255.255.255). CIDR, Subnet Masks, and Usable IP Addresses Quick Aug 26, 2011
Subnetting Reference Sheet
So the subnet mask will be 255.255.255.248. If we use the last octet 248. 256-248 = 8, this means the last octet 0-255 is broken up into 32 groups of 8. Network Address (18 taken from address above) integer(18/8) = 2 * 8 = 16 192.168.4.16 Broadcast Address (18 taken from address above) integer(18/8) = 2 + 1 = 3 * 8 = 24 - 1 = 23 192.168.4.23 255.255.255.0 Subnet Mask for IP Networks - Lifewire Mar 23, 2020
Subnet Calculator for IP Addresses and Subnetting ONLINE!
A Full IP subnet cheat sheet in a table format for your day to day subnetting tasks. IPv4 chart includes cidr, subnet mask, wildcard and IPv6 chart includes number of /48, /56, /64, /127 per prefix