What Is the Difference Between IP Passthrough Mode and Bridge Mode?

When you set up a local area network (LAN) at home, you may run into a situation where you can use IP passthrough mode on your router. Or, bridge mode might be better suited for your purposes. Both IP passthrough and bridge mode have similar functions, but they’re not used for exactly the same. Let’s look at bridge vs passthrough in more detail and see why you would use one or the other.

What is IP passthrough?

IP passthrough is a setting that lets you essentially disable your router without disabling your modem. These days, when you get a modem from your internet service provider (ISP), you have a modem and router combined into a single device. The modem is what establishes your internet connection, the router is what helps set up your Wi-Fi, or local area network (LAN).

If for some reason you don’t want to use the router that came bundled with your modem, maybe because you want to use a different device with higher performance, you can disable it and set up IP passthrough.

When you set up IP passthrough, your public IP address “passes through” to the device you have connected, rather than to the modem/router device your ISP provided you with.

What is bridge mode?

Bridge mode is a setting on your router that lets you connect two or more different networks so they can communicate with each other. Essentially, it’s a way to extend your network to get more coverage. If you want to buy a second router to use as an extender, you’ll need to use bridge mode.

Before going further, let’s quickly explain the difference between a router and a bridge. They were designed to do basically the same thing, which is connecting two networks. However, a bridge connects two (or more) networks by meshing them together to create a larger network. A router keeps the two (or more) networks separate, but gives them the ability to talk to each other.

Your first router, the one that’s built into your router/modem device from your ISP, creates a private network for your devices. If you buy a second router, it also creates a private network. The problem is that these networks can’t communicate with each other because they don’t know about each other (they’re both private). When you enable bridge mode, you can mesh the networks together.

Is passthrough mode the same as bridge mode?

IP passthrough and bridge mode achieve the same result — forming a sort of bridge for your internet connection — but they don’t do it the same way. The main difference is that IP passthrough mode terminates traffic at the gateway (the gateway is your ISP-provided modem/router). Bridge mode does not terminate traffic at the gateway.

What does that mean, exactly?

In IP passthrough mode, your personal router gets the public IP address, but other devices connected directly to the modem/router will get local IP addresses and still be able to connect to the internet through the modem/router’s network address translation (NAT).

In bridge mode, the ISP routes the internet traffic via your modem/router device without carrying out any routing functions. When you set your modem/router in bridge mode, it becomes a “dumb” modem, which simply passes the WAN IP (usually a public IP) to the next device in line, which is typically a router.

When to use IP passthrough

You use IP passthrough when you want to use a specific device on your network, and provide that device with a static IP address. A common example is using another router besides the one provided to you by your ISP.

Since having two routers would create a problem for network address translation (NAT), you have to enable passthrough on one of your routers. NAT is simply a process that lets you map multiple private addresses inside a network before transferring information to the public internet. When you have two routers, you get double NAT, which creates two private networks that interfere with each other. IP passthrough solves this problem.

When to use bridge mode

You would use bridge mode when you want to let multiple routers share one Wi-Fi network. If you connect a second router to your network, both routers will have a private IP address. This makes it hard for devices connected to your network to communicate with each other.

An example is if you want to print an image via your smartphone, wirelessly. Your smartphone is connected to the second router, the one you’re using as an extender. Your printer is connected to the modem/router device provided by your ISP. Since both networks are private, your smartphone won’t be able to communicate with the printer to print your photo. To solve this problem, you can turn on bridge mode on your ISP-provided router.

Advantages and disadvantages of IP passthrough

Advantages 

• Your router still keeps some of its routing functions, like NAT.
• You can pass the global IP address from the Wide Area Network (WAN) to the router.
• Your router is bypassed for a faster, more direct connection.

Disadvantages

• When IP passthrough is enabled, your router essentially acts as a pass-through device, allowing any connected device to access the Internet directly. It disables your firewall and opens you to security risks.

Advantages and disadvantages of bridge mode

Advantages 

• Bridge mode can extend the range of your Wi-Fi.
• You can get good reception even as you move further away physically from the ISP-provided Wi-Fi router.
• You can connect numerous devices while providing faster speeds and improving reliability.

Disadvantages

• Bridge mode disables some traditional router features such as parental controls and MAC address filtering.
• Some ISP-provided routers don’t allow you to bridge them, forcing you to bridge the secondary router instead.

Bridging your network

There are several reasons why you’d want to create a bridge or passthrough on your LAN. Before you do, check to make sure the method you’re using, bridge vs passthrough, is appropriate for your goals. Also, make sure your ISP-provided modem/router can do what you’re planning to do.

If you’re looking for more information about home networking, routers, or modems, check out some of our related articles:

• How to guard your home network
• Wireless network terms you should know
• The difference between LAN and WAN
• What is a subnet?
• What are network devices and what do they do?