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If I put a router in bridge mode, my understanding is that the dhcp function in that router is disabled and the IP address that we receive is actually being assigned by the main router.

My question is if the main router acts as DHCP server for the bridged router, can the wifi broadcast protocol(802.11b/g/n/a/ac) also be taken from the main router? If not, how does wifi devices connected to the bridged router obtain ip address that are in subnet of main router as DHCP is disabled in bridged router? Or is it that the bridged router cannot become an access point?

Please do help me understand. I can be completely wrong also.

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can the wifi broadcast protocol(802.11b/g/n/a/ac) also be taken from the main router?

No, that doesn't make sense. It isn't a data protocol – it actually defines the how the radio signals are generated, so it's hardware-dependent and each Wi-Fi radio transmitter has its own setting for that, because older ones might be physically incapable of using newer modes. (So it is completely normal to have a "mixed" Wi-Fi network where newer APs use 802.11ac but older ones use 802.11n for example.)

The 802.11 mode also has no relation whatsoever to IP address assignment. It just carries data; it doesn't even care whether it's carrying IP in the first place.

If not, how does wifi devices connected to the bridged router obtain ip address that are in subnet of main router as DHCP is disabled in bridged router?

The key word is that it's a bridge – that means it does not create a separate subnet and will transfer any and all Ethernet frames from one side to another. If the device broadcasts a DHCP request, the main router will receive it completely unchanged; likewise for the DHCP response.

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  • "It's hardware-dependent and each Wi-Fi radio transmitter has its own setting for that". Thanks for this info. I actually have a n/ac capable router(my main router) and an old g router(the bridged router) capable of only 54mbps speed. I was hoping to extend my network without degrading my internet speed, but it seems that it is not possible due to hardware limitations.@grawity If you have any better suggestions about how should I use my old g router, that would be really helpful. Dec 6, 2019 at 13:14
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Without direct knowledge of your intended configuration I will try to keep my answer as broad as possible.

If the "Main Router" in your scenario is inside your network (on premise) your router should still be able to pass DHCP.

If the Main Router is located at your ISP(NOC), my experience is they typically only allow 1 IP address reservation for one modem. You would still need a DHCP Server inside your network (or serving your network) in that scenario.

IF your wireless network is a separate subnet(network address scheme) Your router may also be able to provide this using DHCP relay. DHCP Relay allows a DHCP server on one network to supply the DHCP for another connect but unrelated network.

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    thanks for your response. Appreciate it but not really what I was looking for. Dec 6, 2019 at 13:13

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