Forum Discussion
DHCP Setting Incorrect Gateway IP
I've had the Sagemcom Fast 5688W router for about three weeks. I'm fortunate to be near a tower and typically see 5 bars but noticed that I was getting 4 bars and just to see what would happen, I power cycled the router on 5/10/24. When the router rebooted, signal strength was good, but I could no longer connect to the internet from every connected device.
Checking my IP settings I noticed the DHCP assigned gateway IP was 192.168.12.88 while the router's management IP is still 192.168.12.1. For a test, I switched my PC to a static IP matching the DHCP assigned IP and switched the gateway IP to 192.168.12.1 and I was able to connect to the internet.
Definitely a LAN DHCP settings issue as the WAN side is fine. Called into T-Mobile support and the rep was stumped and opened a ticket to investigate. As this will take a few days, I set static IPs on my devices so I can use the working gateway IP. I'm playing in the DHCP scope so I could see an IP conflict but should be ok until this is worked out as device use at my home is pretty consistent.
Firmware is SGJi10205-1.2.B4 and I've only found one mention of this version so far over on Reddit while searching the internet for info. Post was from 18 days ago so this could be a relative new release and I didn't see the issue until the power cycle occurred.
Sagemcom 5688W Firmware Updated : r/tmobileisp (reddit.com)
Anyone else experiencing this?
Testing further over the weekend, I discovered that the 192.168.12.88 IP belong to my Zmodo security camera NVR. And checking "ipconfig /all", my computer indicated the NVR was the DHCP server. Totally odd as I've never seen this happen and the NVR doesn't have settings for running its own DHCP service.
After disconnecting the NVR and power cycling the T-Mobile router, DHCP was working with the proper 192.168.12.1 gateway address. Turning the NVR back on, everything is still working.
It's not a T-Mobile router issue... We'll not quite 100% on that as the NVR has been attached to several routers (Linksys, Netgear, Spectrum) and this is the first time this has happened. Network Gremlins!
@MiddleManagement, a few questions for yo to help with the diagnosis. I have the Sagemcom with the same firmware and all is ok. My setup is: Sagemcom > ethernet to Eero 6+ > 2.5gb switch. The Eero is in bridge mode and allows the Sagemcom to spool out IP addresses via DHCP. All wireless devices connect to one SSID provided by the Eero.
Please describe your setup. Confirming now that your wifi devices can connect to your SSID? Have you tried to reboot your PC/Mac devices?
Basic setup without customization, other than changing the SSID name and setting a password. Devices and the router have been rebooted. All devices connect successfully to WiFi. Two PC's, Two iPhones, two Android Phones & an Android Tablet all pull DHCP straight from the T-Mobile router.
Device IPs - 192.168.12.X
Máscara de subred: 255.255.255.0
Gateway: 192.168.12.88 ← This is the suspect
Router management IP: 192.168.12.1
Change the Gateway IP on the endpoints from 192.168.12.88 to 192.168.12.1 and connections work as expected.
@MiddleManagement glad to hear it. Enjoy!
