General discussion

Locked

subnetting IP address

By schristo ·
I have been given a class C address range from my ISP. I want to subnet it. I want 7 DMZ's which I can get by using 255.255.255.252 subnet mask on the 1st 6 and 255.255.255.248 on the 7th one. I want to split the rest of the IP's into the range of x.x.x.32 thru x.x.x.127 and x.x.x.128 thru x.x.x.255. the .128 thru .255 I can get by using 255.255.255.128, will this also work for the x.x.x.32 - x.x.x.127 range as well? When I run this through a subnet calculator, it says that address ranges .1 thru .127 will be used. If I have a different subnet mask for .1 thru .31 will this be a problem?

This conversation is currently closed to new comments.

5 total posts (Page 1 of 1)  
| Thread display: Collapse - | Expand +

All Comments

Collapse -

subnetting IP address

by bowieb In reply to subnetting IP address

I don't know of any way for you to get that last subnet. The 255.255.255.128 netmask gives you two subnets (1-126 and 129-154). You cannot combine pieces of subnets, you have to take all or nothing.

If you do what you are describing, the machines with addresses 32-126 will not be able to access the machines 1-31 because they will think they are in the same subnet. You may be able to get around this with some fancy routing, but it's really not worth it.

If you need to create a network this complex, I would suggest that you use a private subnet for your network and do NAT translation at the router. This way, you could use the entire 172.16.0.0 class B for all of your machines and then assign the real Internet addresses to machines that need them (such as web servers). Any addresses that are left can be put into a pool for outgoing Internet access for the rest of your machines.

This sounds complicated, but it's really not. And it will give you more room for subnetting (each of your subnets can have a whole class C), as well as some additional security from the NAT setup.

Collapse -

subnetting IP address

by schristo In reply to subnetting IP address

The question was auto-closed by TechRepublic

Collapse -

subnetting IP address

by eBob In reply to subnetting IP address

You can't "overlap" or "extend" (depending on your point of view) subnets. But here's something that will work, assuming that you are using an IP routing protocol that supports VLSM (Variable Length Subnet Masks).

(Assuming your class C is 210.1.1.0)

210.1.1.128 with mask 255.255.255.128
- address range: 210.1.1.129 - 210.1.1.254
210.1.1.64 with mask 255.255.255.192
- address range: 210.1.1.65 - 210.1.1.127
210.1.1.32 with mask 255.255.255.224
- address range 210.1.1.33 - 210.1.1.63
You need to use all three subnet definitions to get the address range 210.1.1.33 - 210.1.1.254. You need to route between these three segments. Alternatively you can (on some routers) define secondary IP addresses. This is OK, but causes overlaps on the physical network which I believe results in excessive collisions, which will impact performance. better to stick with 3 distinct physical collision domains, and try to match a "workgroup" against the size of the subnet.

Finally you can takethe rest of your class C as follows:
210.1.1.0 255.255.255.252
- 210.1.1.1 -> .2
210.1.1.4 255...252
- 210.1.1.6 -> .6
210.1.1.8 255...252
- 210.1.1.9 -> .10
210.1.1.12 255...252
- 210.1.1.13 -> .14
210.1.1.16 255...252
- 210.1.1.17 -> .18
210.1.1.21 255...252
- 210.1.1.21 -> .22
210.1.1.24 255...252
- 210.1.1.25 -> .26
210.1.1.28 255...252
- 210.1.1.29 -> .30

(8 little 2-host subnets)

Hope that helps. For other info on Subnetting, try "learntosubnet.com".

Collapse -

subnetting IP address

by schristo In reply to subnetting IP address

The question was auto-closed by TechRepublic

Collapse -

subnetting IP address

by schristo In reply to subnetting IP address

This question was auto closed due to inactivity

Back to Networks Forum
5 total posts (Page 1 of 1)  

Related Discussions

Related Forums