Help with Sub-netting - Networking - Running out of IP addresses

I know very little about subnetting.  I have taught myself everything I know about Networking which is not too much.
Currently, I have 2 DC (windows 2000) with DHCP Services on them.
Our Workstations are using mostly Static IP addresses but now we have a lot of people brining in PDA's along with Laptops (to connect to our wireless) so I have had to increase the number of reserved IPs for DCHP.
We are running out of IP addresses and I am not sure what to do to increase them.

Gateway: 192.168.0.1
DC1 DNS: 192.168.0.2
DC2 DNS: 192.168.0.3
Subnet is 255.255.255.0

What would happen if I manually changed the DHCP/DC Subnets to 255.255.0.0 ?  
Will I have problems with DNS?
Do I then have to edit the DCHP Sever reservations?  
Do I also have to manually change the Static IP Machines Subnets to match?
On My Router/Gateway: 192.168.0.1 I have included a snapshot of the subnetting options.  When you see the choices for Subnet Mask I don't see an option for 255.255.0.0
What would I need to change on it?

Treat me like Michael Scott (the office): Explain it to me like I am an 8 year old, ok now explain it to me like a 5 year old :)
Thank you For the Help
PM
Gateway-Router.jpg
parmorAsked:
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that1guy15Commented:
Increasing your DHCP scope and subnet is not the best solution for this issue. When you increase the number of IPs on the same subnet you also increase the amount of broadcast traffic on the subnet which can start to cause issues within your network. Plus you will not be able to easily control what traffic gets priority in the future if you need it.

My suggestion if you want to handle the increase in devices correctly is to segregate the traffic into VLANs. You can setup all your local connected devices into one vlan and then all wifi devices into a seperate vlan. Depending on the number of devices you should be able to create each vlan with a /24 subnet.

VLANS basically are segregated networks that cannot communicate with each other but reside on the same physical network. In order for vlans to communicate with each other they must pass through a router or mult-layer switch.

So vlan1 (connected devices) will be ip range 192.168.0.0 /24 and your vlan2 (wifi devices) will be 192.168.1.0 /24.

Im not sure if you are familiar with VLANs or if the switches and router you have will support them but there is a little bit more involvement to it.

If you are interested i can get you pointed in the right direction

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zwart072Commented:
you can make your subnet twice as big, when you change your subnet to 255.255.254.0. You have to do this on your dhcp server and also on your router.
When you adjust your subnet you have 512 ip adresses available.
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JeffSchaperCommented:
I'm also concerned with your statement "Currently, I have 2 DC (windows 2000) with DHCP Services on them."
Use only 1 DHCP service per LAN.
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that1guy15Commented:
Yeah changing your subnet mask to 255.255.255.254 will be a simple fix for this issue. But it is not going to help you in the long run.

You mentioned that you are starting to have people bring in their PDAs and laptops to connect to the network. With the increase in devices you are also going to see an increase in network resource utilization along with your internet bandwidth usage go up.

I can also guess that a lot of these users are using these wifi devices to primary surf the net or use internet resources.

If you have services such as VoIP or web services that your company relies on you will start hearing complaints from employees saying that the internet is slow or my phone calls are choppy etc...

With one big subnet you will quickly find that giving these types of traffic priority over the casual internet surfer from their iPhone difficult if not almost impossible.

Segregate the traffic now so you dont have to deal with as big a mess when it becomes an issue.

Just my two cents.
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JeffSchaperCommented:
Also if the PDAs and laptops are only used / brought in and used occassionally, decrease your DHCp lease time to maybe 16 hrs. This will mean that the addresses will be free the next morning to be issued again instead of being held in a lease that does not need it.
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parmorAuthor Commented:
Wow! I didn't expect this many replies so quickly. Thank you!

I actually do only have one DCHP Service running on DC1, sorry about that.

My Routers (we have 3 - (2) Linksys RV082 and (1) Linksys RV016 and they do have VLANs in the Port Management Section. But they connect to a 48 port Switch so can I do anything with that?

I can change it to 255.255.255.254 on the DCs (DHCP Service) but how do I change it on that Router (the options for the subnet masking were attached in the original post).

Also, will it cause problems across my network if I change the DCs subnet mask?

What IPs will be availabe with the new subnet? 192.168.X.X - 192.168.X.X ?

Do I have to manually change all Static IP PCs/Xerox Machines Subnet to 255.255.255.254?

Re: The PDAs and Notebooks: Most of them are used for just browsing and checking their email but there are a couple that need access to Network Resources.
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parmorAuthor Commented:
Im not sure if you are familiar with VLANs or if the switches and router you have will support them but there is a little bit more involvement to it.

If you are interested i can get you pointed in the right direction:

that1guy15:
Thanks I would be interested.  

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Chris DentPowerShell DeveloperCommented:

> Do I have to manually change all Static IP PCs/Xerox Machines
> Subnet to 255.255.255.254?

I'm sure you want 255.255.254.0 there. The other is really not a very big subnet at all, whereas this will give you a scope containing 510 usable addresses (512 in total) :)

A typo I'm sure :)

Chris
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JeffSchaperCommented:
And yes, all static addresses would have to be changed one by one. Including the router and switches servers. This would mean some down time.
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parmorAuthor Commented:
Thanks again all.

I am still a little confused about the actual usable IP addresses. I know with:
192.168.0.1
255.255.255.0
I have 192.168.0.1-192.168.0.254

When I change it to 255.255.254.0, what are the actual usable addresses?
Sorry if it is really simple.
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Chris DentPowerShell DeveloperCommented:

That'll give you:

192.168.0.1 to 192.168.1.254 (inclusive)

Chris
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parmorAuthor Commented:
Thanks Chris-Dent!

One last thing. On the Linksys Router I will have to Choose Multiple Subnet Setting and add LAN IP ADDRESS 192.168.0.1
Subnet Mask 255.255.254.0
so I will have the default of 255.255.255.0 and the manually enter one of 255.255.254.0, correct?
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that1guy15Commented:
yeah sorry about the typo the mask should have been 255.255.254.0. this would give you the range mentioned above by Chris.

If you could give me a layout of how your network is created and what devices connect to each other and how you connect up to the internet, i can give you a more detailed layout and how to proceed.
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JeffSchaperCommented:
No, all subnet mask settings should be 255.255.254.0 especially on the router. If your linksys router cannot handle 255.255.254.0 subnet mask leave your subnet settings alone or get another router which will.
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parmorAuthor Commented:
Excellent!

Primary DC running DHCP (win 2000)
Secondary DC (win 2000)
3 Routers that connect all workstation to internet :
Gateway 1 - Linksys RV016
Gateway 2 - Linksys RV082
Gateway 3 - Linksys RV082
4 - 48 Port Linksys Switches (SRW248G4)
Plus within the Server Room and also the Shipping Room a few other switches that connect some servers  to Xerox Machines (4 of them).

The reason we have 3 Routers is another topic but the fact is right now we have to have them.
Does that help?
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that1guy15Commented:
Could you give me a layout of what switches connect to what routers? Also which switches provide wifi.

Basically I need a network diagram of what your network layout is along with what devices connect to each switch.
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JeffSchaperCommented:
I'd give my addresses similar to the attached text doc.
Subnet-Setting.odt
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parmorAuthor Commented:
JeffSchaper:  Basically I cannot do anything with the limitations of my current routers correct?
Attached jpg.
Or is there something that I am missing with those settings?
subnet.jpg
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JeffSchaperCommented:
What if you click in the Multiple Subnet box then click on the Add / Edit button. It should give you the option to enter the new subnet mask that was suggested by Chris (255.255.254.0).
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parmorAuthor Commented:
JeffSchaper : 04/08/2010 - 01:04PM PDT
No, all subnet mask settings should be 255.255.254.0 especially on the router. If your linksys router cannot handle 255.255.254.0 subnet mask leave your subnet settings alone or get another router which will.

Jeff: I am confused because you said I couldn't do that now you say I can.
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JeffSchaperCommented:
Sorry, I was referring to the post about "so I will have the default of 255.255.255.0 and the manually enter one of 255.255.254.0, correct?" If you are able to add the recommended subnet mask then you have no problem. If it cannot be added then you should not change the subnet. Pls confirm that the recommended subnet mask can be added.
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parmorAuthor Commented:
I have a choice from the drop down menu and the below that I have a choice to add multiple subnets and I can input anything in that option.
Does that make sense?
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JeffSchaperCommented:
Yes, and then it is best to add the new subnet mask and you will be right with your changes.
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parmorAuthor Commented:
Excellent. Thank you. I will work on it.
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parmorAuthor Commented:
Before changing every pc of hardware I can just change the DCs, Router and some static ip workstations just to test, correct?and if they all work and can communicate then change everything, correct?
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Chris DentPowerShell DeveloperCommented:

Yes. As long as you don't add hosts onto the newer part of the subnet you should be fine. Clients using the old mask will only be able to talk to clients on the old range.

If that makes any sense...

Chris
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