subnet question 2

[eanda10]

what is the right way of adding more then 255 machines to my network?

currently we are using the subnet mask of 255.255.255.0 (ip range of 193.100.100.XXX) but i am runing out of internal ip address what is the correct way to add more machines ? and what potential issues are there?

 

[SLMHC]

Subnet your systems.

ie
10.1.1.X
10.2.1.X
and so on...

What kind of network hardware do you run?

thanks,

Dave

 

[eanda10]

can you please explain what you mean by subnet my network

we are running both pcs macs network printers nas switchs and linux servers

 

[SLMHC]

I am not sure how to do in with Linux but within Windows you can setup IP Subnets.

IE
In our hospital we have 8 different sites. We use VLANs to subnet them all, 10.1.1.X, 10.2.1.X etc...

We use DHCP to create scopes for each subnet...

i am not the guru you need, im sure some google searching will help you...i hope ive pointed you in a good direction...

thanks,

Dave

 

[PSWired]

Eanda,
You'll need to create multiple sub-networks on your network. If you're using a private address space such as the 10.0.0.0, 172.16.0.0, or 192.168.0.0 ranges, and a subnet mask of 255.255.255.0, your subnet field would be the third octet of the IP address. For example, 192.168.1.0 would be one subnet, 192.168.2.0 another, etc. When you create multiple subnets you need to have a device to route between them. You'll likely be suited best by a layer III network switch, which can act as a router and connect your subnets together to allow communication between them.

 

[chieftan999]

The simplest way is as PSWired stipulated above.

Lets say you have an IP address of 192.168.25.25 and you used a subnet mask of 255.255.255.0. What this means is that the 192.168.25 section is masked so it becomes the network portion of the IP address and the last .25 is the host address.

Because you can only have 255 addresses for each octet, then that means from a host perspective you can only have 255 with the subnet mask 255.255.255.0. So in thw above example your range of available addresses would be 192.168.25.1 -> 192.168.25.254.

To create more addresses you need to use another network address range......you do not necessarily need to create a seperate subnet....depends what you wnat to do.

An example:-

192.168.15.32 using a 255.255.0.0 subnet mask (Simple one.

Network address is 192.168 and the host portion now becomes 15.32.

As can be seen with the above example this gives you a lot more available host addresses.

Hope this helps

 

[Parcival21]

It seems for me as if you are being provided with a range of public adresses (193.100.100.0 255.255.255.0).
If you are connected to the internet and all your pc's need to connect to the internet you basically have two possibilities if you are running out of adresses. One possibility would be to ask your provider for more public adresses. The other possibility would be to use NAT (Network address translation on your router).
With the second solution (surely the cheaper one), you will only need a few public IP addresses. For the rest you can use a private IP network subnetted like pointed out in the above threads. These addresses will not cost you any money.
THe private addresses will be translated to public addresses on the router.

bye, busche

 

[eanda10]

193.100.100.xx is our private internal ip address when the network was the designed many moons ago the guy who did it selected 193XXX for some odd reason we are currently using NAT on ur router to mask our internal ip address.

-- Thanks

 

[TimRegester]

If your external (so called dirty side) IP address adverised to the Internet and any other connected agency is not 193.100.100.xxx that is noone external to your Network gives a hoot, then you could use 193.100.101.xxx 255.255.255.0 as a second subnet. You then have some nice issues to solve.

1) How to route between the subnets? The easiest solution is a layer 3 switch, that can route between VLANs and shift the amount of traffic to be routed between them. Create 1 VLAN with the 193.100.100.xxx subnet with a VLAN interface address of the default gateway of your this subnet. Create a second VLAN with the 193.100.101.xxx subnet again with the def g/w as the interface address. Create a third VLAN with the internet and other routed connnections, say in a subnet of 193.100.99.xx and remove the 193.100.100.xxx address from the router. Configure the switch to route but do not use RIP 1 (in fact no route advertisement is needed at all on the 193.100.100.xxx and 193.100.101.xxx VLANs) this should enable any device in the correct VLAN to see the internet connection and all devices in each subnet.

2) configure any DHCP servers to provide the right addresses on the right VLANs and if using only one DHCP server config
the switch to forward DHCP traffic.

3) position your servers where they are best placed in either VLAN.

Using the 193.100.10x.xxx range is not ideal but unless all devices have DHCP provided IP addresses there is no need to switch to a 192.168.x.x. or 10.x.x.x scheme. The above method should be least destructive. Watch out for changing Network printer addresses, sometimes the ARP cache get's confused.

I hope this helps.

 

[Serbtastic]

The easiest way to add more host IP addresses is to open up the subnet mask. So instead of using 255.255.255.0 you would use 255.255.0.0, which would then allow for over 65000 valid IP addresses (193.100.0.0 - 193.100.255.255) with no routing involved.

 

[TimRegester]

However If the devices used static IPs all would need changing manually, incurring a significant overhead in terms of time and resources. This is why this a less useful solution unless DHCP is used throughout. Also you would limit the broadcast domain of the whole network if you VLANed the network. Flat Networks beyond 500+ hosts are, in my experience, never a good idea.

 

[Serbtastic]

I agree about the 500 hosts, but you could use a more restrictive subnet in that case (eg. /23), and if most clients are windows, you could use a script to change the mask value (using the 'netsh interface ip set address' command).

 

[eanda10]

Thanks for all your responses

 

[tmt7734]

If you change your mask to 255.255.254.0 (/23) (this is called supernetting) you will have 510 usable host addresses. Keep in mind that this is not best pratice on networks because of the increase in broadcast traffic. Although this is not as big of an issue with switches as it was when we all had hubs.

 

[Serbtastic]

The accepted term these days is Classless Inter Domain Routing or CIDR (supernetting is what it used to be called). And as for broadcast traffic, more hosts would increase broadcast traffic, regardless of whether you use switches or hubs.