Nick_Parker Posted February 27, 2008 Posted February 27, 2008 Our DHCP is set to assign IPs with the following settings: IP: 192.168.0.x Subnet: 255.255.255.0 With a lease time of 7 days (to try and stop old addresses from filling up the leases etc...) According to the scope statistics, we only have 4 addresses left, which is a problem, because 20 new laptops have just arrived (40 potential IP leases, one for wired, one for wireless) What is the best way to go about adding another range to our DHCP server? I read somewhere on this forum that one method would be to add another range of 192.168.1.x and to change the subnet on both ranged to 255.255.254.0 Is this correct? Thanks for your help!
tmcd35 Posted February 27, 2008 Posted February 27, 2008 Is there a reason for currently using 192.168.0.x, apart from it being a well used private range? Are you now deeply tied into using this range - ie, loads of servers/switches/ap/printers/etc with static IP's that'd be a complete arse to change? If not then you may want to consider switching to class B addresses: 172.16.x.x with a subnet 255.255.0.0 - This'll solve your problem not only for now but far, far into any forseeable future, which must be a good thing.
Nick_Parker Posted February 28, 2008 Author Posted February 28, 2008 There are a few static printers/switches/APs, however, if your recommend this as the best option, then i'm happy to spend a weekend changing them over... Would this mean anything in the 172.16.x.x range is valid and viewable?
tmcd35 Posted February 28, 2008 Posted February 28, 2008 (edited) Exactly, this give you something like 65000 valid IP address. If it was my network I'd split these further into logically smaller subnets and only allow the DHCP server to lease a small number of IP's. Thus: say - 172.16.1.x for servers 172.16.11.x for switches 172.16.51.x for AP's 172.16.101.x for DHCP - everything outside of this range is excluded in the DHCP server. If I need more than 256 leases, then I'd un-excluded the 172.16.102.x range. Remember, because the subnet mask is 255.255.0.0, that everything on all the above ranges can see each other, your not making actual physical subnets, your just making it easier to manage your IP's. You could try and work out better subnet mask to shrink the available range of IP's, but unless you paranoid about others hacking your network it's rearly not work it. Also, I've noticed your DHCP lease is 7 days. A bit long if you ask me! Are all the computers in the school likely to be on at the same time? Our lease here is a couple hours (i think). So when a laptop is switched off it's address is freed for another machine. Reducing your lease time could in itself create the extra IP's you need without extended/changing your current range. We have to pay for our IP ranges from county here. They use the 10.x.x.x class A subnet and 'sell' us a subnet for our school from within that range. This means when (were close) run out of IP's (again) we have to pay for another range! I did set up a NAT sever and use my own class B IP's the last time we ran out, but county did not like my solution! I'd give anything for the freedom of my own totaly private subnet. Edited February 28, 2008 by tmcd35 extra detail on DHCP lease 1
FN-GM Posted February 28, 2008 Posted February 28, 2008 What you have to pay for the IP address? that’s robbery! We are fine here, well within our range. We use also use 172. Our range is 172.24.32.0 – 172.24.35.254
tmcd35 Posted February 28, 2008 Posted February 28, 2008 What you have to pay for the IP address? that’s robbery! Tell me about it! Part of using our LEA as our ISP...
zag Posted February 28, 2008 Posted February 28, 2008 Paying for internal IP addresses?? Now I've heard it all Just increase your subnet to .252 instead of .255, that will give you 1000 extra IP's right away. 1
raufdean Posted February 28, 2008 Posted February 28, 2008 Just increase your subnet to .252 instead of .255, that will give you 1000 extra IP's right away Absoulutley. 2 second job. Just have to add my incredulity at the fact that you're paying for private IP space.. Rauf
projector1 Posted February 28, 2008 Posted February 28, 2008 Paying for internal IP addresses?? Now I've heard it all Just increase your subnet to .252 instead of .255, that will give you 1000 extra IP's right away. the good old CIDR (classless interdomain routing!)
cookie_monster Posted February 28, 2008 Posted February 28, 2008 (edited) A few LEAs do this now (and some charge for it) so that all of their schools are on a semi private network, i don't think we do under EMBC but i'd have to check the details of the package. I'm not totally surprised that they would charge for more addresses as they would then have to pass on the work to Fujitsu or whoever to make the changes and they wouldn't do it for free i suspect. County hate it when you use a NAT box as it gets in the way of their plan for world domination (and they can't nosey into your network), they also point out that all of the great services that they 'DON'T' offer will be degraded by using NAT. As you're using your own internal IP range the suggestion of a custom net mask is a good solution. Edited February 28, 2008 by cookie_monster
Geoff Posted February 28, 2008 Posted February 28, 2008 If you are in one of these brain damaged LEAs that charged for private IPs, I suggest you grab a NAT firewall (Smoothwall express, IPCop, DIY Linux, ISA server) and do things that way. If you have anything that 'needs' to be addressable externally, you can use the DMZ functionality. Cheaper in the long run and more secure.
Nick_Parker Posted February 28, 2008 Author Posted February 28, 2008 Paying for internal IP addresses?? Now I've heard it all Just increase your subnet to .252 instead of .255, that will give you 1000 extra IP's right away. If I change the subnet to .252 What IP ranges are then usable?
Nick_Parker Posted February 28, 2008 Author Posted February 28, 2008 Never fear, figured it out, found a very nifty site, helped me work through my moment of dimness! http://ipcalc.nmonitoring.com Thanks to everybody that helped and thanks for all your suggestions!
Nick_Parker Posted February 29, 2008 Author Posted February 29, 2008 I have another query please, If i setup multiple Scopes, how does the server know which one to lease addresses from?
Grommit Posted February 29, 2008 Posted February 29, 2008 We have to pay for our IP ranges from county here. They use the 10.x.x.x class A subnet and 'sell' us a subnet for our school from within that range. This means when (were close) run out of IP's (again) we have to pay for another range! I did set up a NAT sever and use my own class B IP's the last time we ran out, but county did not like my solution! I'd give anything for the freedom of my own totaly private subnet. All you do is get a server and put in 2 network card... Put the 10.x.x.x facing the LEA and then the 172 internal and then set the DHCP to 172.. You then have your own range
tmcd35 Posted February 29, 2008 Posted February 29, 2008 All you do is get a server and put in 2 network card... Put the 10.x.x.x facing the LEA and then the 172 internal and then set the DHCP to 172.. You then have your own range I did that, got told off, the Network Manager bought another range from county!
PiqueABoo Posted February 29, 2008 Posted February 29, 2008 The charge for PUBLIC IPs out in the real-world is supposed to cover administration costs. LEAs are probably (no guarantee) doing exactly the same thing when "selling" private IPs. There is work involved in handing out addresses, sorting out routing etc... and if that is sub-contracted to commercial orgs, that'll be who you're ultimately paying. It's a trade off between that cost and the cost (+ other potential benefits) of how much time it will take to throw in your own NAT box and configure everything you need to run across it properly. I suspect difficulties with the latter is one reason why county/LEA might hate schools with NAT boxes.
Nick_Parker Posted February 29, 2008 Author Posted February 29, 2008 We are in South Africa, we don't have LEAs (to be honest, I don't even know what that is or what it stands for) and so we don't have to pay for IP Leases What I meant was I can setup one scope, say, 192.168.0.x for Servers 192.168.1.x for WiFi Routers 192.168.2.x for Printers 192.168.3.x for PCs So theoretically, i would only set 192.168.3.x to actual have addresses available for leaseing, all the others would have to be set manually and have static IPs. but what if I wanted to introduce 192.168.4.x for laptops Is there anyway I can setup something somewhere or somehow so laptops are assigned from 192.168.4.x and PCs from 192.168.3x Thinking about it, I would say no, there is no way of doing without manually setting each IP (static IPs).
Nick_Parker Posted March 1, 2008 Author Posted March 1, 2008 Or you would setup a revision for them. A revision?
FN-GM Posted March 1, 2008 Posted March 1, 2008 Yes. In DHCP you make a new record manually, and you put a mac address of the device and then assign an IP address. You set the device to pickup a DHCP IP address and every time it asks for an IP from the server it will get the one you assigned. 1
Nick_Parker Posted March 1, 2008 Author Posted March 1, 2008 Yes. In DHCP you make a new record manually, and you put a mac address of the device and then assign an IP address. You set the device to pickup a DHCP IP address and every time it asks for an IP from the server it will get the one you assigned. oooh, a reservation Yes, that would work, but I don't really want to create 100+ reservations for the laptops & their wireless connections
PiqueABoo Posted March 1, 2008 Posted March 1, 2008 We are in South Africa, we don't have LEAs (to be honest, I don't even know what that is or what it stands for) LEA = Local Education Authority RBC = Regional Broadband Consortium Don't know/think it's universal in the UK, but in this context one of the above is running what is typically a big private intranet and school networks are connected to that. There will likely be serious firewalls between the intranet and Internet, central web caches, DNS, time services etc. Because managing that intranet takes effort a school may well have to pay for getting new blocks of IP addresses, which is just the same getting IP addresses when you have a public connection from an ISP (in either case that cost may be hidden in some annual charge rather than explicit). LEAs tend to be a school tech's psychological "out-group", the common enemy they can get together and whine about. Sometime's that is justified, sometimes it's just whining. You often see the same effect further down the food-chain i.e. teachers/staff vs. school techs. Anyway... I think having ranges for statically configured devices is sensible (printers, servers, WAPs, switches etc.) but I wouldn't bother trying to distinguish between laptops and PCs via their IP address - you can do that with their computer name/DNS e.g. LAPTOP-27, SCIENCE-03, OFFICE-01. If you must have different IP addresses for Laptops then I'd be thinking about putting the wireless infrastructure on a separate (routed) subnet.
localzuk Posted March 1, 2008 Posted March 1, 2008 The problem is, the DHCP server has to distinguish between a printer, a desktop, a laptop etc... How can it know other than via a manual list of MAC address reservations (or, if you wish to not use static IP's, via an IAS server, managed switches and MAC address authentication)? Somehow, the server would have to be told what devices get what. The small scale way of doing this is to create reservations. The large scale way is as I stated above. I have an IAS server which looks at a list of allowed devices when a computer connects to the network. It then assigns it to the relevant VLAN and from that the DHCP server knows which DHCP scope to serve an address from. However, I don't pay attention really to the IP addresses for identifying machines, as computer names are much more useful. I implemented the above to provide some form of authentication and to segment the network. 1
FN-GM Posted March 1, 2008 Posted March 1, 2008 If i was you i would have 3 ranges. 1 Range for Static IPs (Such as servers etc) 2 Ranges for DHCP Clients
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