198.22.45.173/26

64개 호스트

173 (10진수) -> 10/10111 → subnet mask 128+64 = 192 173-128=45 45-32=13 13-8=5

255 - 64 = 191

198.22.45.128 ~ 198.22.45.191

network addr = 198.22.45.128

boradcast addr = 198.22.45.191

vaild host addr = 198.22.45.129~198.22.45.190

subnet mask = 255.255.255.192