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Are too many subnets a bad thing?

By TenHaken ·
We have the oportunity to redesign our IP addressing scheme due to a corporate MPLS project.
In the past we had no IP restrictions and currently use one LARGE subnet for our office and management PC's and servers, with a few smaller subnets for the smaller manufacturing and remote sites.
My question is this. Can I use subnets to manage groups of computers based on physical location, rather than resource use? In other words, even though most of our office PC's/printers, are accessing servers in the data center (and this would be the busiest segment), can I subnet by building and floor (physical location) without an impact on performance? Should I keep the servers in the same subnet with the PC's that access them?
We will be 'given' a range of addresses, and I need to determine what we need to ask for (so we can compromise...)
My Admin would like to keep the layout as simple as possible, but he does like the idea of being able to associate a specific IP subnet to a specific location.
Any suggestions are appreciated. Thanks!

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by overwrked1 In reply to Are too many subnets a ba ...

Using subnetting as a management tool is a good idea for different locations that exist outside of the physical location of the resources. As for systems located at the same location subnetting is usefull only if you are supernetting them together and you have a very good DNS structure so the systems can find resources easily. Using the names of the systems for describing location is a better idea as numbers and people don't mix well. Use a naming convention that describes the location simply such as WS21W23C123, workstation 21 wing 2 3rd floor cubicle 123. This is much easier to dispatch a technician to than if something is broken. Subnetting can add delay to any route when used in a single location since the default gateway must determine the correct network both ways from the routing table. As for IP addresses and your ISP they usually don't give out more than a partial "C" subnet to anyone without major justification so you'll be using a private address range and NAT more than likely. Make sure the range you pick (class A B or C) will allow for growth and the remote locations and you'll be ok.

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by TenHaken In reply to

Thank you. This was very helpful, as I wasn't aware of the overhead associated with the added routing tables. I think we will be given 10. /24 addresses, so having a couple subnets in one location may be inevitable, but we will try to group them by resources then.

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by TenHaken In reply to Are too many subnets a ba ...

This question was closed by the author

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Subnetting is basically location independent

by onlineguy In reply to Are too many subnets a ba ...

Please keep in mind that IP addressing is completely virtual "Layer 3" stuff... they are just numbers... however it may make sense in your setup to consider using an addressing scheme that takes "workgroups" or locations or other organizational considerations (e.g. i/o devices like printers, wireless vs. wired, etc.) into account.

Cisco always used to recommend using a hierarchical form for subnetting, with the "access" IPs being aggregated using Layer 2 devices (i.e. Ethernet switches), hence the term "workgroup switch."

The basic idea is set up (designate, using an appropriate subnet mask, etc.) a subnet for EACH major org. division and then populate the IP space on workgroup switches, with each plugged into a router (which can move traffic between Layer 3 routes, aka logical or IP addresses).

Some of this complexity has been obviated by 'Layer 2/Layer 3 switches' which accommodate both needs in one device--and by using advanced centralized autoconfiguration, speeding up the admin process, but it's still worthwhile to conceive and map out your network with close attention to whatever will a) get the job done, and b) offer sufficient room for growth until your job description is likely to change (2-3 years?).

The resources you expend on doing the network correctly now should pay untold dividends as you have it working smoothly, unlike many poorly-designed/managed corporate nets I've encountered over the years. Good luck! May the force (money) be with you... and don't waste thousands on equipment or help you don't need. You can probably get a sharp certified Cisco or other ntwk consultant to map out your net better than doing it yourself if you've never done it before, too.

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