Subnetting

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So i have a question - at work were using a 172.17.0.0 /21 private address - we've got an absolute **** load of spare address's - at a rough guess i'd say we have approximately 5000 spare address just on that subnet, i've been asked as junior person to rack everything up for a 10.10.0.0 /21 - ok fine, but isnt that exactly the same as working with a class b address?

Anyway i've been asked to take intop account we may well need more subnets and maybe about 3000 ip's for one particular project. I suppose whats happening is were expanding - but my thing is - how is it any differant using a 10.10.0.0 /21 than a 172.17.0.0 /21 address - apart from it looks differant - if we need to expand we could - dare i say it move newer stuff up to 172.18.0.0 /21 if we need to, upper management are talking about supernetting but i dont think we need to - why would we unless were about to buy the whole internet and if we do i'd like my broadband untracked... Can anyone give me an example of when they had to supernet ? i mean i thought about it and thought maybe u plan a range - suddenly u expand quickly - u wanna keep it tidy so u break the subnets down more, or i'm not sure - or maybe i'm missing the point - part of me is saying were just creatng extra work for ourselves to goto a 10 range ? but i'm the junior so i'm just doing what i'm told anybody else come across this sort of thing?

 

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actually i think i'm missing the point...more reading needed

 

At one place I worked, we had configured the following ranges for our sites:

10.0.32.0/23
10.0.35.0/24
10.0.36.0/24
10.0.39.0/24
10.0.41.0/24
10.0.43.0/24
10.0.44.0/24
10.0.45.0/24

Okay, so that means there's 510 addresses available in the 10.0.32.0/23 range. But what if we had to expand beyond 510 hosts? Moving to a /22 range by using 10.0.32.0/22 range would conflict with the site using the 10.0.35.0/24 network.

Same thing for the 10.0.44.0/24 and 10.0.45.0/24 networks; if we ever needed to expand past 254 addresses, we would have had to reallocate an entire range one way or the other, because 10.0.44.0/23 encompasses both ranges.

This is why careful planning is required for each subnet range.

Not sure why your company wants to move from one private /21 range to another private /21 range... the only benefit to using a Class A private IP range (10.x.x.x) is that you're limited to a /12 or larger subnet mask with a Class B private IP range (172.16.0.0 to 172.31.255.255). But you probably don't need a /12 anyway! After all, the 172 range gives you over a million addresses to play with.