single ssid

Ranju wrote:

OK let me try to explain!

I have Tmobile ssid “xyz” same for both 2.4GHZ and 5GHZ and that is fine, SSID is enabled for both.

 

Now I have configured Netgear extender for 2 SSID "xyz_2GEXT" and "xyz_5GEXT". Both keep dropping.

xyz_2GEXT says couldn’t find IP address

xyz_5GEXT says log in to network and prompts for admin user and password (log in does nothing for underlying message)

Netgear says it is bandwidth conflict so give different names for 2.4GHZ and 5GHZ on router.

I think it should work as is, single SSID for router and 2 for Extender.

Ok, thanks.  I can't get detailed with some of this since I dont know what the model of the netgear repeater is. It sounds like you might have multiple errors, or one error could be causing the other.  These are my initial thoughts that might help resolve both of these error messages.

From the two different errors you mentioned you may have two different issues. I believe that might be because the T-Mobile Gateway is using a some sort of signal strength monitoring for smart connect. This is what they say in the T-Mo gateway manual:
“The gateway automatically steers client devices to the best band and
channel combination for most situations.”

If your netgear extender is extending the 2.4Ghz and only one of the T-Mobile 5Ghz channels so I would suggest turning off the second 5Ghz channels that is enabled on the T-Mobile gateway by default. From the above found in the manual it sound like the gateway will sometimes pass off between the low and high channels of the two 5Ghz radios with its smart connect algorithms.
The gateway runs a 5Ghz high channel and 5Ghz low channel enabled by default. So on the gateway either turn off SSID5 (low 5Ghz channels) or turn off SSID9 (high 5Ghz channels) so if the gateway is passing the repeater between the two 5Ghz radios this will stop that from happening. Also I don't know what model of repeater you are using, but this might apply to your model as well?
https://kb.netgear.com/25346/What-is-Smart-Connect-and-how-do-I-enable-or-disable-it-on-my-Nighthawk-router

IP Address Error:
As for the client IP address error this could be from the gateways DHCP renewing IP policy. I find it better when running multiple main networking equipment to just assign the IP's manually/static. This also makes it easier to connect with the web gui interface by that static IP instead of using some app that searches for the devices.
Note: It might also be from lost connection with bandwidth error as I will explain in the next part.
If can you assign the IP's to the netgear repeater manually? I believe it might be two IP's, one for the 2.4Ghz repeater radio and one for the 5Ghz repeater radio. Usually it would have to be two differnt IP's since each radio should have a different hardware MAC address.  I have my one device manually/static assigned as:
IP Address: 192.168.12.2
Subnet: 255.255.255.0
Default Gateway: 192.168.12.1
So if its for each radio the IP would be 192.168.12.2 and 192.168.12.3 and the subnet and gateway would be the same for each one.

Bandwidth Message Error 5Ghz:
The T-Mobile gateway also uses Auto Bandwidth as the default for each of the radios. You would have to look at the specs of the netgear repeater to see what the 5Ghz repeater bandwidth is using. If this is a WiFi5 (AC) repeater then its probably using 80Mhz on the 5Ghz radio. Some WiFi6 (AX) radios can use 160Mhz bandwidth, but the T-Mo gateway can only do up to 80Mhz.
NOTE: If the repeater is an older WiFi that has the 5Ghz N it might only do 40Mhz bandwidth, but without knowing the model of the repeater I can not look up the specs for it.
In this issue you shouldn't have to change anything on the repeater. Assuming its a WiFi5/WiFi6 repeater (AC/AX) you can set the T-Mo gateway bandwidth manually so it wont try to Automáticomatically change the bandwidth. The repeater will stay at the same manual bandwidth you set on the gateway.
If its a WiFi5/WiFi6 (AC/AX) repeater then under the 5Ghz on the gateway change the “Ancho de banda del canal” from “Automático” to “80Mhz
If its an older G/N with 5Ghz repeater then under the 5Ghz on the gateway change the “Ancho de banda del canal” from “Automático” to “40Mhz

T-Mo Gateway 2.4Ghz Bandwidth:
I would also set the T-Mo gateway 2.4Ghz radio bandwidth from Auto to manually use 20Mhz. The 20Mhz is best practice with 2.4Ghz since 2.4 does not have that many channels and is a cleaner signal when your in an area that has other 2.4Ghz radios running. 
NOTA: All apple devices and some other manufacturers only use 20Mhz when connecting to the 2.4Ghz frequency for this reason.
Bluetooth is also on the 2.4Ghz spectrum, specifically channel 9 of the 2.4Ghz. For this reason  usually assign the 2.4Ghz channel manually between channel 1 and 5 so it does not overlap on channel 9. This way the WiFi on 2.4Ghz wont interfere with Bluetooth and vice versa. You might be able to find a free or cheap WiFi scanner app to see what channels the neighbors are using and make sure your 2.4Ghz is not overlapping on channel 9.
Also if you have the repeater close to a microwave the microwave also operates on a 2.4Ghz spectrum and can cause the repeater to disconnect.

Finally NetGear Smart Connect:
I also found this about, it applies to range extenders listed on the right side of the page but also might apply to yours? This shows how to disable the smart connect feature on the extender. Since you are using different SSID's for your 2.4/5Ghz extender the smart connect should be turned off.
https://kb.netgear.com/000044734/How-do-I-enable-or-disable-Smart-Connect-on-my-Nighthawk-Mesh-WiFi-Range-Extender
 

In the end if these suggestions don't fix the issue you may have to just also separate the T-Mo gateway 2.4Ghz and 5Ghz SSID's to be names the same as you have it on the repeater. If you have mobile devices like phones/tablets/laptops it should automatically hand off between the T-Mo gateway and repeater as your devices move around the house. This is how most repeaters are designed to be used, but it's not the first time I have used something in a different way by changing settings like the way you are trying to do.

Let me know how it works out for you,
Scott