DHCP on two different interfaces

aileron · Dec 16, 2017, 7:17 AM

Hi!
I run pfSense 2.4.2_1 on an embedded box with 4 NICs. Two of those are configured as failover WAN, the other two are connected to two different and separated networks. Both of those interfaces run a DHCP server providing addresses of two different networks, 192.168.0.0/24 and 192.168.10.0/24. However, no matter to which network a new device is connected, it always receives a 192.168.10.* address, even if it's connected to the interface that should provide 192.168.0* IPs. Somehow the DHCP request seems to be received and answered by the wrong interface. I have checked the network setup and configuration a couple of times and still cannot find the cause.

Anyone has an idea how to fix this?

johnpoz · Dec 16, 2017, 8:40 AM

And what are these interfaces connected too - a switch? The same switch?

aileron · Dec 17, 2017, 11:49 AM

The interfaces are connected to two separate switches, of course. There is no physical connection between the two networks other than the pfSense-box.

johnpoz · Dec 17, 2017, 2:32 PM

Do you have anything that connects these 2 switches together.. If your using different switches, and there is nothing that connects these switches together then what your saying is happening is impossible..

So you either have these switches connected together and joining the layer 2. Or you have something else that is connected to both switches that is bridging the networks at layer 2. Or 3rd option you have some other dhcp server running on this network that is handing out the wrong address for that network, etc.

You don't have your interfaces bridged on pfsense do you? You don't have something wired to one switch and wireless to network on the other switch that is bridging these - sonos speakers for example?

If they are really not connected together than something else running dhcp is likely.. You forget to turn off dhcp server on some old wifi router your trying to use as AP?

Gertjan · Dec 17, 2017, 4:53 PM

Also check this :
When connecting to a network (is interface) you should see these line in the DHCP log :

Dec 17 17:40:31 dhcpd DHCPACK on 192.168.2.9 to 90:b9:31:77:5e:26 (iPhone-5S-Gertjan) via sis0

sis0 is my OPT1 interface (NIC), using 192.168.2.1/24

When I connect my phone to my LAN (using an AP on my LAN) I see this :

Dec 17 17:46:38 dhcpd DHCPACK on 192.168.1.21 to 90:b9:31:77:5e:26 via fxp0

fxp0 is the device name of my LAN NIC.

Both my internal NIC's fxp0 and sis0 have separated DHCPv4 server setup pages.
With the correct pools etc.

Also : isn't this some f*cked up "gateway" issue, knowing that you have 2 WAN's ? (delete one WAN completely - you have then a setup like every one else) and re test.
(this is more a wild shot from me - as I never sued dual WAN setups before)

johnpoz · Dec 17, 2017, 4:55 PM

multiple wans could have ZERO to do with it.. Zero… He could have zero wans, or 100 wans nothing to do with dhcp servers running on lan side interfaces..

Basic layer 2 problem here.. Either he does not have his networks isolated like he thinks, or he has some other dhcp server running on that layer 2 handing out the wrong network ip range.