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Wrong DHCP server responding

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bathcentre

IS-IT--Management
Aug 23, 2011
2
GB
Hi... we have two networks - one for the PC's (192.168.10.x) and one for our Mitel 3300 phone system (192.168.2.x). The networks share a Netgear FVS124G firewall/router and some switches. We have always set the PC's up with static IP's and left the phones to sort themselves out with the Mitel DHCP server on the 2.x network.

Now, we want to add wireless to our PC network so visitors can get Internet access on their phones or laptops at our premises. We have connected a Netgear WNDAP350 wireless router (plugged it in to the other router) and set it up as a DHCP server with a scope on the 10.x network.

Unfortunately, the result is that sometimes clients join the 10.x network and sometimes they join the 2.x network. This wouldn't be so bad, but with some clients, joining the 2.x network doesn't give them Internet access, we think because the Mitel server doesn't hand out any DNS server addresses (although it has one listed in its settings). Some clients don't mind this, and some, notably Apple iPhones and iPads, and the occasional PC, do mind. Blackberries tend to just work whichever network they join.

Anyway, we would like to find a way to get clients to join the 10.x network, without ruining the phone network (it hasn't happened yet as far as I know, but I suppose it may be possible for a phone to join the 10.x network). I tried blocking BOOTP protocol on the FVS124G but it made no difference. I have also tried reducing the scope on the Mitel 2.x network so there are only enough IP addresses for the exact number of phones, but in fact that doesn't work reliably either: possibly I need to reduce the number further than I thought, but anyway, it will be a constant nuisance having to edit settings whenever a phone is added or taken away (which does happen as offices get rearranged pretty often).

We are considering re-wiring our setup to separate the two physically but haven't worked out the consequences of that yet: it may be that something depends on the current arrangement that we are not aware of. So, short of that, is there anything else we can try? TIA...
 
Are you not using your WAN port on the router and just hooking every thing through the LAN ports? If so that could be messy. You might even have computers (depending on the TTL) on your private network get IPs from this DHCP server.

Personally I would just configure the device as a WAP and use a VLAN to the edge router so that their traffic does not go through the private network but it could be your switches do not support VLANs.
 
Hi - yes, the WAN port of the router goes to a Cisco router which in turn goes to an SDSL line.

It seems to me it would be possible for PC's on the private network to get IP's from the phone system's DHCP server, but we set them all with static IP's. Perhaps this is why, indeed: it was set up before my time.

I tried giving the DHCP scope a VLAN index in the wifi router, but it made no difference: broadcast requests for an IP address get a reaction from both servers (the wifi router, and the phone system) and accept whichever offers first.
 
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