dhcp server question

"-keevill-" hath wroth:

That doesn't mean that the answer will be simple.

Are these wireless *ROUTERS* or are they *WIRELESS ACCESS POINTS*? Better yet, kindly disclose the maker and model numbers.

Yep. You can get away with it by using non-overlapping IP blocks and a large netmask, with a common gateway IP. However, there are a few situations where it will screwup. For example, if the client roams to a different wireless router, and then tries to renew the DHCP lease, it will fail because the lease can only be renewed by the DHCP server that originally issued the lease.

No clue or guess. Kindly disclose the maker and model numbers along with the topology (wiring and interconnections). There are several ways to configure such a system. Some will work, some will not.

Why don't you have the "main office router" act as the DCHP server? That way, you don't need wireless routers and can use wireless access points.

No clue. I need to know the hardware and topology.

Intermittent success is not very successful. My guess(tm) is that your clients are roaming to different wireless routers, which is causing problems.

You can. You just can't roam between access points with such an arrangement. If you have all your wireless routers set for the same SSID, you won't even know if a client has roamed until it tries to renew the DHCP lease, and fails.

In case you missed it.... Make, model, harware version, topology, etc.

They are wireless routers SMC2904wbra2 All have different SSID's They are wired with RJ45 cables running from an initial Router ( same make and model ) which itself is connected to the ADSL Internet connection. I think it's fair to say very simple topography. There should be no need for PC's to roam between routers but of course some will be able to contact 2 routers. Hope that's enough for some ideas of best way to manage things.

"-keevill-" hath wroth:

Google does not find that device number. Could you verify that this is the correct number and possibly supply a URL?

Good. Then they won't roam.

The main router obviously has the WAN port connected to a broadband modem of some sorts. The LAN ports probably go to the 4 other boxes. Are you connecting these 4 cables to the WAN port on the 4 routers, or to the LAN port? It makes a huge difference.

With different SSID's, a user can select the wireless router of choice.

Well, I think you should do it like this:

1. Setup the IP address of the 4 satellite routers on different sequential IP's. For example: 192.168.1.1 main router 192.168.1.2 satellite router #1 (...) 192.168.1.5 satellite router #5 Each satellite router (access point) must be on a different IP address in order to properly manage and monitor them.
2. Disable the DHCP servers in the 4 satellite routers. The only DHCP server running will be in the main router.
3. Setup the DHCP server in the main router for a range of: 192.168.1.100 thru 192.168.1.149

50 IP address should be enough.

1. Run the CAT5 cables from the 4 LAN ports on the main router to one of the *LAN* (not WAN) ports of the 4 satellite routers. This effectively converts them into wireless access points. The router section is disabled and not used. No cable goes ot the WAN ports.
2. Setup the 4 satellite access points on different RF channels (1,

6, and 11) but with the same SSID. Since they have the same default gateway and the same DHCP server no matter which access point a user connects, the DHCP renewal process will work.

Why?

If all your devices (laptops, pcs, etc) are connecting to the same subnet then it's often best to use a single DHCP server. If they're all on the same network then you HAVE TO do this. If they're on different subnets (and there are plenty of good reasons for/against this) then you'd want to look into DHCP forwarding. The wifi devices are configured as routers. Each expecting to have it's own subnet behind it. As in, the main network is

192.168.5.0 and the wifi networks are on, say 192.168.12, .54, .120 and .188. They could be on any numbering, nor does it matter their sequence. You'd then configure them to DHCP forward any requests to a central DHCP server on the main 192.168.5.0 network. On that DHCP server you'd setup ranges for them (.12, .54, .120, .188 or whatever). This way you get a central place to administer all DHCP settings.

Alternatively you could configure the wifi units as access points. Here they act as passive connectors, any hosts connecting to them are granted DHCP from whatever DHCP server is active on the wired network. The main network tracks which device is on which wifi access point based on ARP tables (stuff you normally never see).

There are a number of different scenarios that might be applicable here. You'd have to better describe what your network and users need before deciding what sort of scheme is appropriate. This ends up being more of a generic networking question than wireless.

-Bill Kearney

They are all on the same subnet

192.168.0.xx They all connect to the same network "mynetwork" Each wireless router is acting as access points - since they are each connected via LAN cabling from the ADSL modem / router into on of their LAN sockets ( not WAN ). So, I am sure I read it correctly that I must turn off the dhcp on each of the access points and turn it on ONLY on the ADSL modem/router. Users connecting to each access point will be able to get an IP address via this 'central' DHCP server . Many thanks for help from both posters.

-keevill-

A quick check, you do not have more than 254 devices there do you? If you did then you'd need to get into different subnet planning. Move to a class B, the 172.16.x.x range is just for that purpose.

I take it by this you mean the SSID are all the same?

Yes, that's what should happen.

Only about 40 devices max !

No this means they all connect to the same Domain / Workgroup

No they are all slightly different .. 'router_1' ' router_2" etc etc I am toying with the idea put up by another post where I use the same SSID but different channels...

Ok, just make sure your DHCP settings allow for that many hosts. Some have a smallish range setup by default.

Also consider that low-end Small-Office/Home-Office (SoHo) gear does not handle a lot of simultaneous traffic very well. They're targeted toward the small network with under a dozen devices, max. The reason is the firewall on them doesn' t have enough memory or CPU to keep too many sessions running at the same time.

Each time you open a browser and surf to a site you're opening up, usually, around 8 sessions (some more, some less). Multiply that across multiple hosts and you run into trouble. One way to alleviate this is to run a proxy server internally. This funnels the computers through a more controlled number of sessions. There's a free one called Squid that's worth considering (available on linux, windows, etc). You may want to keep this in mind should network traffic get out of hand (which it inevitably will).

-Bill Kearney