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To have an IP Passthrough option on a Wi-Fi router from an Internet Service Provider (ISP) means that all the internet traffic is bridged through any device on the other end of the router (any device connected to the LAN port of the router LAN).

This is a very handy feature to have especially when there’s a device attached to the router and you wish to have the global IP address from WAN on the router. Through this setup, port forwarding becomes so much more convenient.

In simpler terms, IP Passthrough mode deactivates the functionality of the router and assigns the cellular WAN address straight to any of your desired devices connected to the router.

IP Passthrough setup in the router assigns or routes the IP address allocated by 4G/3G network to an inbuilt firewall (Juniper, Cisco, etc.), router, or computer. This mode is appropriate for any device that needs to directly get the WAN IP address.

It also arranges for Network Address and Port Translation (NAPT) or Port Address Translation (PAT) through the cellular network IP address. This 4G/3G IP address is also allotted and reused on a LAN computer.

What is the IP Passthrough Mode?

IP passthrough is a setting in which your modem hand off your static IP address to some other equipment piece. It operates basically just like the bridge mode where users can utilize their own router behind the gateway provided by the ISP.

However, in the IP passthrough setting the signal is cut off (as compared to the bridge mode where the signal is not ended) at the gateway and enables the ISP to link with the gateway with its own IP address.

The internet traffic though will still pass through the gateway, and the public IP address given by the ISP will be assigned to the router of the user.

IP Passthrough Configuration – Step By Step

Here is how you can configure IP passthrough on AT&T and other routers:

  1. Open a browser on your PC that’s connected directly to the gateway.
  2. Paste http://192.168.1.254 in the address bar.
  3. Choose the Firewall tab on the RG GUI page.
  4. Below the tab, choose IP passthrough.
  5. In case you’re prompted, insert the Device Access Code.
  6. From the drop-down menu of the Allocation Mode, choose the Passthrough option.
  7. Choose DHCPS-dynamic from the drop-down of passthrough.
  8. Tap on Save and a reminder message will appear.
  9. Choose Restart Now and refresh the network. 

What is a Bridge Mode?

Bridge mode is a configuration that enables the NAT feature on your modem and allows a router to function as a DHCP server without any IP address conflicts. Connecting various routers would extend the coverage of Wi-Fi in your home.

The gateway provided by your ISP is a combination of a modem and a router. In some cases, instead of the router built in the gateway, users want to use their own router.

To get this setting, an ISP may set the gateway to a “bridge” mode, and routes the internet traffic via gateway without carrying out the routing task.

When you enable bridge mode, the router function (layer 3) is essentially disabled and the gateway function is converted to a modem (layer 2). Since you’re changing the gateway to a layer 2 device, a static IP address to your gateway can’t be assigned in bridge mode.

As no traffic is being filtered, the NAT feature can’t be utilized in a bridge mode setting. However, the DHCP server service offered in most bridge mode routers can still be used. Moreover, because you’re deactivating NAT on your gateway, you will not face a double NAT error with the personal router you may have linked with your gateway.

A double NAT issue arises when you have two systems needing to be present in the same LAN, but originating from two different subnetworks because of two routers. Perhaps, this is one of the main reasons why you may wish to set the gateway in bridge mode to elude the double NAT problem.

IP Passthrough – FAQs

Bridge mode does not cut off the traffic at the gateway. On the contrary, IP passthrough mode does terminate traffic at the gateway. For internet service providers to bypass the gateway, the bridge mode should be avoided and IP passthrough mode must be used.

No, IP passthrough isn’t recommended while gaming as enabling this mode on the modem will cause substantial lags while gaming. It is recommended to disable IP passthrough while gaming.

In layman’s terms, the IP Passthrough mode enables a device on the LAN to get the public IP address assigned to the router. It also offers PAT and NAPT through the same public IP for every host on the private LAN subset.

Conclusion

Both the bridge mode and IP passthrough modes perform the same function where all of the internet traffic is routed through the gateway and the public IP address is assigned to the router of the user operating behind the gateway.

In bridge mode, traffic is not terminated at the gateway, whereas, the traffic is terminated at the gateway in IP passthrough mode. For ISPs to link with the gateway, the IP passthrough setting should be used rather than the bridge mode.