2 DHCP servers on the same network

Riddle me this: A BT Quantum Phone system has a built in web server for administration and configuration. However it also contains a DHCP server that cannot be turned off and a static IP address that cannot be changed. I would like to put this device onto the network so that I can administer the phone system remotely; however the network already has a better and more manageable DHCP server and uses a different IP address range. The network also issues public IP addresses to internet facing devices. The network contains a layer 2 managed switch, so it is possible to put it on a separate vlan, and I suppose I could use a PC with a vlan capable network card, RDP into it and then use IE to connect to the phone system, however I am looking for a better solution maybe some kind of a bridge that allows translation between the two networks blocking each other’s DHCP packets. Anyone have any suggestions?

Robin

Posted 2013-02-08T13:18:47.823

Reputation: 11

3Call Quantum Phone system and tell them you want the DHCP turned off? Either they tell you to edit some configuration file, edit the binaries or get it logged as a critical feature request. Only after that fails try to work around it. – Hennes – 2013-02-08T14:00:02.557

@Hennes is right. You cant be the only person to buy this system with an existing DHCP server. – Keltari – 2013-02-08T19:53:57.603

Answers

I think putting the BT Quantum phone system on a seperate VLAN will solve your problem, but I don't see why you would need a VLAN capable network card in your PC or RDP. Simply ensure your router can route between the 2 VLANS (which will have different subnets, as you say they use different IP ranges). [ IE ensure your router is configured as the gateway for each network and have it route between them ]

I do find it questionable that a device has a DHCP server and Static IP address which can't be changed - you should definately explore the reasoning behind this as there is almost certainly "more to it" then meets the eye and it could be beneficial to know the limitations/logic upfront. (Maybe the phones need to be on the same subnet as the phone system to work ?)

davidgo

Posted 2013-02-08T13:18:47.823

Reputation: 49 152

Thanks for your answer, I asked the BT engineer the same question about the DHCP and he says it is to do with the base unit. A slightly different model has the ability to become a ADSL router with a DMZ and internal network output, however because this version is missing the DMZ output the firmware throws an error when you try to change either of the options! I don't think that the router will work with VLANs as it is a BT Business hub (similar to the home hub but more business orientated firmware). I am going to try and use a cheap cable router and see if I can perform a bit of NAT magic... – Robin – 2013-02-20T21:51:35.700

Its a limitation with the Quantum - the port is used purely for configuration and as such is not designed to be networked. If you wanted to network the Quantum you should have bought the Fuse model which is designed to be networked.

user204089

Posted 2013-02-08T13:18:47.823

Reputation: 1

the problem is with that is I cant configure / monitor the system remotely, if it was not designed to be networked they shouldn't have put an RJ45 port on it! We also want to be able to look at the call logs, I don't want to go to our server room every 10 minutes to look at them... There is no reason that BT could not fix this in the firmware so that it knows there is no DMZ port, it may even be fixed in a later revision of firmware however without a service contract (and I suspect even with one) it is very difficult to obtain. – Robin – 2013-03-08T21:21:31.350