I was trying to do an exercise where we have a range of IPv4 addresses and we need to convert it both to "prefix notation", e.g. a.b.c.d/x, and to "address/mask".
Now, apparently, the following range 121.34.56.64–121.34.56.128 can neither expressed in prefix notation nor in address/mask. Why is that? I mean, they have the first 24 bits in common, so I would express the range as 121.34.56.64/24 in prefix notation.
Other ranges that I do not understand why they cannot be assigned a prefix notation and an address/mask notation:
- 128.131.9.0–128.131.9.192
- 93.20.10.0–93.20.11.0
- 128.242.138.0–128.242.139.127
Maybe I am just confused about how these prefixes and masks are obtained. So, in general, which ranges cannot be expressed in prefix notation and prefix/mask notation? Is there a time where it is possible to express a range in prefix notation but not in prefix-mask (or vice-versa)?