DGN2200v3: External DHCP server not working over WiFi

[terrybarnaby]

I have a home network with 3 WiFi routers each having a different SSID. One of these is a DGN2200v3 with DGN2200v3-V1.1.00.24 firmware and that one performs ADSL internet connection duties. The DHCP server in all of these WiFi routers is disabled. The network is 192.168.2.*.
I have a main Linux server that provides DHCP, DNS and other services to this network. This was all working fine until the replacement of an older DGN2200v1 with the DGN2200v3.
The problem is that WiFi clients (Linux PC's and Android phones) can connect to the DGN2200v3 but do not receive their IP address via DHCP. Sometimes they do connect and get IP address, but if those clients are connected to a different WiFi router and then try to reconnect to the DGN2200v3, they will fail. The Linux server is getting the DHCP requests and replying but they are not getting through the DGN2200v3. Connecting to either of the two other WiFi routers (DHC2200v1 and 585v3) work fine.
I have tried a lot of things on the DGN2200v3, changing config, changing back to older firmware, (.23) resetting the configuration, disabling iptables rules etc all to no avail. I assume the DGN2200v3 is not listening for Ethernet packets destined for the WiFi client.
Any ideas ?

[Babylon5]

You could check the Wireless Isolation setting, maybe even enable it / apply, then disable / apply. If this is enabled it will isolate wireless devices from the LAN, but allow Internet access. If isolated from the LAN then they will not be able to see the DHCP server replies.

[terrybarnaby]

Thanks for the reply, the Wireless Isolation setting was off. I did try turning it on and then off. No effect.
If you retry connecting to the DGN2200v3 WiFi on from a client after a time (hour ?) then it works. If you then disconnect and reconnect to one of the other WiFi access points and then disconnect from that and retry to connect to the DGN2200v3, it fails at the getting IP address stage.
It seems that once disconnected from the DGN2200v3, or perhaps once connected to a different WiFi router the DGN2200v3 disregards Ethernet packets on the LAN sent to the client for a period of time. Wireshark running on the server shows the DHCP request and DHCP response packets fine.
Seems like a firmware bug in the DGN2200v3 V1.1.00.24 firmware to me.
Anyway to debug this on the router (I have telnet access)

[terrybarnaby]

Further to this I have found that the router will start working again after about 3 minutes. So something is timing out within 3 minutes.
I have installed tcpdump on the DGN2200v3 to try and see what is happening. Using:
"tcpdump -i eth0 ether host xx:xx:xx..."

This shows the DHCP requests going out but nothing coming back when DHCP fails. I see the DHCP replies when it works. So I assume either the MAC packet filtering on eth0 is wrong or the packets are not getting to the router. There is a Netgear GS116E switch between the server and the WiFi routers.

[terrybarnaby]

Has anyone else had a DGN2200v3 working as a WiFi access point with other WiFi access points on the same network where DHCP is supplied by a server on that network ?

Form my work on investigating this issue, I think this is a bug in the DGN2200v3's firmware. I have tried to contact Netgear via their on-line support system but all I get is a response saying my 90 days of free support is up. I am trying to report an issue/bug on a Netgear router that has probably been there since purchase and hopefully get it fixed, how do I accomplish that ?

[terrybarnaby]

I have looked at the bridge operation using:
"brctl showmacs group1"
This correctly shows the clients MAC address moving from port 1 (Ethernet) to port 5 (Wifi) when the WifI client tries to connect to the DGN2200 after being connected to a different WiFi router. So the DGN2200's bridge is seeing the device move ...

[terrybarnaby]

I have updated the firmware on the GS116E switch, just in case (saga in itself). The problem still exists. I set the GS116E switch to mirror the port the DGN2200v3 is connected to, to a machine running wireshark to make sure the DHCP offers are actually on the Ethernet wire to the DGN2200v3, they are.

So it looks like, for some reason, the DGN2200v3's Ethernet interface is ignoring/filtering the external DHCP offers and not sending them out over the WiFi once it has seen packets from the client device coming from the Ethernet interface (It has been attacher to a different WiFi router).

Has anyone any ideas ? Netgear appear to be no use what so ever as the unit is greater than 90 days old and they cancel any support requests I put in (unless I pay for someone who I suspect doesn't know low level details such as this and spend a lot of my time with them paying for the privilege).

Has anyone actually managed to get the DGN2200v3 working with another WiFi router on the same network using an external DHCP server and allowing the WiFi clients to switch between WiFi routers ? It seems to be that there is a bug in the DHC2200v3 firmware that prevents this. Is there anyway to report this issue and/or get someone in Netgear to actually look at this ?

[bluesteam]

Really interesting!  seems everywhere I look on the net, everyone who is trying to do this with the netgear routers are having this problem.  I'm also having this EXACT issue now.  Seems Netgear is ignoring this problem!