Two routers (one wireless) who should be providing DHCP services?

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lchiu7

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# 38027 23-Jul-2009 12:03

I have a router/switch connected to an external Internet connection (dedicated line). The router (a Linksys RV042) has 4 ports on it. It's replacing a DSL line so we also have a Netgear ADSL modem/router/switch in place.

I want to retain the wireless capability but of course the Netgear can't be used as a router anymore. So in a test I disconnected the RJ11 and connected a port on the Netgear to the Linksys. Now the Netgear was serving up addresses in the 192.168.0.x range while the Linksys uses 192.168.1.x.

Just using DHCP the PC I attached to the Netgear, got an address in the 0.x range and so it could not access the Internet until I hardcoded an address in the 1.x range. That is not useful as you can imagine.

Should I just leave both devices doing DHCP and change the range of addresses to be the same on both or disable DHCP on one device (possibly the Netgear) and let all addresses be resolved by the main router?

Any ideas appreciated

Thanks

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rhysb

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# 238204 23-Jul-2009 12:08

You'll need to disable one of the DHCP servers. You cannot have two DHCP servers on the same lan segment.

lchiu7

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# 238210 23-Jul-2009 12:27

I realise that. But should I also change the IP address of the wireless router to be in the same range as the main router? At the moment it's not. Does it matter?

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magu

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# 238236 23-Jul-2009 13:44

You have a somewhat dysfunctional setup.

What I do in cases like yours is to set the main router a 192.168.0.1, the access point as 192.168.0.254 and enable only the DHCP on the main router, not the AP. Also, make sure you're NOT using the WAN port of your access point (if it has one), but one LAN port to connect it back to the main router (either directly or through a switch).

IP addresses are examples, of course, as I prefer the 10.x range.

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nate

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# 238281 23-Jul-2009 14:33

lchiu7: Should I just leave both devices doing DHCP and change the range of addresses to be the same on both or disable DHCP on one device (possibly the Netgear) and let all addresses be resolved by the main router?

Disable DHCP on one device, specify your IP range with a few static assignments (say 192.168.1.20 to 192.168.1.254). You can then use the lower range for any static devices such as photocopiers, web servers, wireless APs etc.

cr250bromo

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# 238291 23-Jul-2009 14:46

I agree in this case is it is best to turn one of the DHCP servers off.

However it is possible to have two DHCP servers on the same subnet, as long as they have different pools which can be useful for failover.

EG one DHCP server may give out 10.1.0.1 - 10.1.0.50 and the other may give out 10.1.0.51 - 10.1.0.100. For static assignments via DHCP you code them into both, ie 00:1a:b1:c3:d5:b1 might be mapped to 10.1.0.150 on both dhcp servers.

magu

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# 238294 23-Jul-2009 14:54

Not a lot of DHCP servers on these routers support static assignments outside their scope (or address pool), so make sure you test it thoroughly.

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lchiu7

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# 238296 23-Jul-2009 15:04

I ended up doing the following.

1. Left DHCP on with the main router (which is connected to our dedicated Internet connection) with internal address 192.168.1.1

2. Turned off DHCP on the WAP which has an internal address of 192.168.0.1

The main router is connected to a main switch and also to the WAP

With some preliminary testing it seems wireless and wired clients are getting their addresses from the Linksys router and still able to access the Internet okay. So things appear to be fine.

The only issue is we cannot manage the WAP without changing the IP address on a PC to be in the right subnet but that's not thing we would do that often.

Thanks to all who commented

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tonyhughes

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# 238307 23-Jul-2009 15:58

magu: You have a somewhat dysfunctional setup.

What I do in cases like yours is to set the main router a 192.168.0.1, the access point as 192.168.0.254 and enable only the DHCP on the main router, not the AP. Also, make sure you're NOT using the WAN port of your access point (if it has one), but one LAN port to connect it back to the main router (either directly or through a switch).

IP addresses are examples, of course, as I prefer the 10.x range.

I see OP has got a resolution sorted, but for future readers, I give a "+1" to this scenario from magu.

lchiu7

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# 238413 23-Jul-2009 19:43

Yes I might change the WAP address to 0.254. That means I can still manage it and I know DHCP will never give a client this address.

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