1

I want to setup a network with about 1000 users. I have access points with no DHCP servers in them. So, I think I might have to put a DHCP server on the network. How can I do that?

4
  • Don't you already have a router which has a DHCP server? Just make sure its network is setup is a /22 (/16 might be simpler). Aug 3, 2016 at 6:38
  • Please clarify this question, otherwise it will likely be closed. Yes you need a dhcp server if you want to issue IP addresses via DHCP.
    – Paul
    Aug 3, 2016 at 6:39
  • As paul said we ned more info. Whst OS are your clients and future DHCP running? Are your pcs joined to a domain? Are you planning on splitting up broadcasts with vlans or routers if there is too much broadcast traffic with 1000 devices?
    – Lister
    Aug 3, 2016 at 7:05
  • Most likely whatever device that is acting as your gateway will also have the capability to be a DHCP server. You should be able to access the webui and turn on DHCP and specify the range of IPs you wish to hand out. As Lister points out, you also need to be wary of your current network config - most SOHO devices default to /24, which doesn't have 1000 addresses, so you may need to reconfigure your network with a larger network segment.
    – MaQleod
    Apr 30, 2018 at 23:14

1 Answer 1

4

To begin with, we have to decide what range of IP addresses we are going to use. How many IP addresses do we need, will we need more in the future?

Because you want over 256 clients, the 192.168 range is not technically appropriate, even though you could do it. the 172.16 range is also reserved for private use, and gives us more than we need (It gives us 65534 usable Ip addresses.)

So lets create a subnet mask that covers what we need. Our subnet mask will begin with 255.255 to represent that 172.16 shows us our network portion. To cover off 1024 hosts we only need 10 bits (IP addresses are in binary, there are 32 bits in total.) But lets use another to cover off potential growth.

If we use a mask of 255.255.248.0 that will represent 2048 ip addresses (2046 of them are usable) Then we have the following:

Subnet ID 172.16.0.0/21
Range 172.16.0.1 - 172.16.7.254
Broadcast 172.16.7.255

So thats our IP range sorted. Now all we have to do is install a DHCP server of our choice (If you give us details on which one I can improve my answer.) and give the DHCP server that range. It will start allocating on that entire range. We can also configure the DHCP server to give clients other options including setting up their DNS servers, but again that is OS specific.

This next part goes beyond the scope of your question a bit, but is important for those wanting to build large networks and may not know what they are heading into. 1000 Hosts on one network is a lot. Every host sends out broadcasts messages including arps (Hey who's 172.16.5.3.) If you have a lot of clients and they are all broadcasting then you are going to get a lot of traffic.

This is where VLANS/Routers come into play. You can segregate your devices into broadcast domains. What this means is we could break down our 172.16.0.0 subnet into smaller subnets, say /24s This means that any one on 172.16.0.0 can talk to eachother, but not to any one on 172.16.1.0 without the help of a Layer 3 Device (Router or a layer 3 switch if your using VLANS.) If a device broadcasts, only 253 other devices will hear that broadcast, rather than all 1000 of them.

There is an entire Cisco course on the topic (CCNA/CCENT) which covers this, and I would recommend if you are planning such a venture that you take the time to at least read the course material, it will stand you in good stead.

2
  • "Because you want over 256 clients, the 192.168 range is not technically appropriate" Why not? There is no restriction on how you can subnet 192.168.0.0/16. CIDR lets you have any size prefix from /31 (point-to-point links) all the way down to /16, and still remain in the Private Addressing.
    – Ron Maupin
    Apr 30, 2018 at 23:40
  • "the 172.16 range is also reserved for private use, and gives us more than we need (It gives us 65534 usable Ip addresses.)" The 172.16.0.0/12 Private Address range give you 20 bits for host addresses (1,048,576 host addresses), which can be divided from /31 to /12. Also, RFC 1918 actually recommends using the 10.0.0.0/8 range ofver the smaller ranges, subnetted as necessary, unless you have devices that cannot use subnets (very unlikely with anything in this century).
    – Ron Maupin
    May 1, 2018 at 0:24

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .