I am revising some questions for an exam and one of the questions was provide the ip numbers and a diagram for a company which has 3 branches. Paris/Berlin/Cairo (random locations I know) Now I belive I have figured out the answer but I would appreciate someone checking as my brain is fried and I think if this answer is wrong I won't be able to see that's its wrong.

You have 3 routers which means 6 networks All should be /24, the IP addresses should resemble 10.12."network number"."host number" ie 10.12.59.1, so that its a /24 that means the mask is going to be 255.255.255.0, so my host ranges are, not including broadcast addresses

- 1-30
- 33-62
- 65-94
- 97-126
- 129-158
- 161-190
- 193-222
- 225-254

So I could use 6 of them for my 6 networks, 1 for each of the branches and 1 for the 3 networks joining the branches.

The Berlin branch network is extended with 2 additional VLANS. These networks should be sub-netted from 10.12.59.0 with a /27 structure. Now this is where I start to know I am weak in my knowledge. the mask for a CIDR/27 is 255.255.255.224 but I cant figure out how to implment a /27 numbering within a /24 network. Can anyone explain please?