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Subnetting

Discussion in 'Routing & Switching' started by morph, Jun 26, 2008.

  1. morph

    morph Byte Poster

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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?
     
    Certifications: Network +, ITIL Foundation, CCENT, CCNA
    WIP: server/ccna security
  2. morph

    morph Byte Poster

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    actually i think i'm missing the point...more reading needed :)
     
    Certifications: Network +, ITIL Foundation, CCENT, CCNA
    WIP: server/ccna security
  3. BosonMichael
    Highly Decorated Member Award

    BosonMichael Yottabyte Poster

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    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.
     
    Certifications: CISSP, MCSE+I, MCSE: Security, MCSE: Messaging, MCDST, MCDBA, MCTS, OCP, CCNP, CCDP, CCNA Security, CCNA Voice, CNE, SCSA, Security+, Linux+, Server+, Network+, A+
    WIP: Just about everything!

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