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Restrict DHCP?
Hello Everyone,
Thanks for taking the time to read this.
I've got a Netgear Orbi Mesh router with one sattelite.
Everything was fine until 3 days ago when the cable modem I own was replaced with an Altice One (Suddenlink) cable modem.
Ever since then, the Orbi is handing out IP addresses from the new cable modem instead of it's own range from DHCP.
Is there a setting somewhere that I can force it to only use it's own DHCP IPs?
So far only WiFi devices are affected. The hardwired devices seem to be OK, though most of those devices I have set for static IP addresses...
TIA!
OK, first off, you don't have to be a **bleep**. You made a short answer, being "no, you can't" into this whole big long thing and have been throwing shade for most of your replies.
Second, I'm asking if this device will do something that many other devices do. Just because you don't like the question, doesn't make it the wrong one.
Third, I intentionally left off the make/model of the modem to minimize the "Have you tried doing this?" posts that I didn't want. As if I hadn't tried any of the things y'all would've said to log into the modem to try. The cable modem given to us from Altice One needs the DHCP on and the WiFi on for the DVR's to work. Period. Turning those functions off is not an option.
Lastly, I've managed to solve the issue by setting up VLANs on the Cisco switch so that the only devices getting an IP from the cable modem are the DVR devices.
You can reply if you like, but I'm done with this post, and most likely the community as well.
Good day.
20 Replies
what altice one modem?
It doesn't happen to have its own integrated router does it?
StephenCG wrote:Ever since then, the Orbi is handing out IP addresses from the new cable modem instead of it's own range from DHCP.
Do you state the Orbi system does allow to "leak" a WAN/Internet side DHCP server (in your case the one on your new cable modem) randomly or always, instead from the one on the Orbi router LAN/WLAN side? I doubt somehow this is possible on such a consumer device. If yes, you can bring your iptables knowledge back in here.
Please provide us the IP subnet from your old cable modem (probably 192.168.0.0/24) and the IP subnet you had seen on on the on the Orbi system (probably the Orbi default 192.168.1.0/24) before.
And then to compare, provide us with the IP subnet in use by the new ISP provided modem/router/gateway, and the IP subnet on your Orbi router LAN/WLAN.
I suspect your new ISP supplied cable modem does run by default on the IP subnet partially or in all detected as overlapping with the IP subnet you had previously configured on the Orbi LAN/WLAN. Is it possible the Orbi has adopted the LAN subnet on it's own because it detected the same or a similar IP subnet overlap situation. Needless to say - routing would not work on the same or a partially overlapping IP subnet of course. And (not a secret): I've seen this isn't very reliable on the Netgear routers for certain non-standard environments.
The point is that Orbi does just retain the second half of the fixed DHCP table - the network part does change along with the Orbi local subnet.
StephenCG wrote:Everything was fine until 3 days ago when the cable modem I own was replaced with an Altice One (Suddenlink) cable modem.
Ever since then, the Orbi is handing out IP addresses from the new cable modem instead of it's own range from DHCP.
Is there a setting somewhere that I can force it to only use it's own DHCP IPs?
Sorry to be "late to the party", and I understand the problem has apparently been resolved. I find that this forum frequently exposes my lack of expertise in "how things work", and am wondering if this is one of those situations.
The problem description is not consistent with my understanding of the Orbi and DHCP. Devices get IP information (address, subnet mask, gateway, DNS servers, etc) by sending out a DHCP broadcast and accepting the results from the first server that answers. (In corporate environments, there are often multiple DHCP servers, but that's another situation.) When the Orbi is operating as a router and is set to provide DHCP (on the Orbi web interface, Advanced Tab, Setup, LAN setup, "Use router as DHCP server", then those broadcasts do not pass through the Orbi. The Orbi responds to the device with DHCP information. The Altice One will never see the broadcasts, and will not respond.
If a device is connected to the Altice One rather than the Orbi, then the Orbi will never detect the DHCP broadcasts, and the Altice One will respond with whatever DHCP settings it is configured to supply.
If, for example, both the Altice and the Orbi have the same WiFi SSID and password, then devices could be connecting to one or the other and get different DHCP responses. It is not clear (to me) how this would happen simply by replacing a modem.
So, I am at a loss to understand the problem.
