Ubuntu DHCP central server

Question

I have very little experience on this so I am asking to see if this is even possible. I have 4 different ADSL connections that each one is connected to one access point so I have 4 total different lans. I provide free hotspot on each access point (same SSID) and the user roaming from one access point to the other as they move into the area. (The area is a long road and the distance beetween each AP is about 100m). Anyway i saw on the modems the option for dhcp relay so I am asking this.

Can I build a central server (internet accessable) with ubuntu and dhcp server on it and setup the modems to use this as DHCP server? So the user keep the same IP as it moves from one AP to the other. All adsl modems will have the same IP so the gateway will remain same for all networks. I dont know if this is good so I am asking this question just to tell me what is the best way? To build a central server or to leave each modem act as dhcp server

Because my English are not very well I hope you understand my question

Thanks a lot!

Answer 1

This can be done, but I don't know if it will provide any benefit to you:

User comes online from AP1, DHCP discover is received by the modem and relayed to the DHCP server, response is sent back and the user receives and binds to IP.

User crosses the threshold and changes to AP2. Because the media has changed, the user will re-discover and perform the DHCP process again. They will most likely be allocated the same address again (presuming the lease hasn't expired or been administratively removed), but you're still re-binding the IP. Because you are re-binding the IP on the User, any open TCP connections would likely be severed.

I think that this is what you're trying to avoid by allocating the same address across all devices, but please do correct me if I'm wrong.