Old Router, New Provider: Will the Old Router Still Work?

By SB •  Updated: 06/25/21 •  8 min read

Wondering if your old modem or router will work with your new internet service provider? It depends on:

  1. the type of modem you have, and
  2. what kind of internet service will be supplied by the new service provider.

If you are currently using a combined modem-router for a DSL service (for example), and you are switching to a new ISP for the same DSL Internet service, most likely your old modem, if it is compatible with the new network, will work with your new service. It will need to be configured by your new ISP, but this is often a hands-off experience for you and it is a task performed by the new ISP or a contractor at the line level. Sometimes it will require logging into your internet gateway and adding new ISP-supplied credentials.

People often use the terms “router” and “modem” interchangeably, but they are not the same device (though they can be combined into one combo device).

The main difference?

What does a Modem do?

Summary: A modem is a bridge between the infrastructure (cable, fibre optic, DSL or satellite) of your Internet Service Provider (ISP) and your Ethernet cable output that you can connect to a router or computer. For fibre, DSL and cable connections, a single cable from your ISP is the input, and an Ethernet cable is the output. Different ISPs have different compatible modems that that will work with your specific connection input.

Routers, however, can be chosen freely as their input is the standard Ethernet cable.

What does a Router do?

Summary: A router creates your local are network (LAN). With or without an Internet connection, a router’s primary function is to connect multiple devices and/or networks, and manage (route) all traffic between them.

For example, all devices connected to a home router can communicate amongst each other, wired or wirelessly — this is great for sharing a printer or a media server among all your home devices. However, a router is most often used to provide your local network with a connection to the Internet, and enable multiple devices to use the same Internet connection.

Combining Modems and Routers

So, you can see that a router and a modem are two separate devices. Because households commonly have many Internet-capable phones and computers and media streaming devices, routers and modems are commonly integrated into one combo device, for convenience and savings. But these combo modem-routers are not always great at performing both jobs, and depending on your network needs, buying a separate dedicated router is usually the way to go.

Switching Providers For the Same Internet Type

Can You Still Use Your Old Modem or Router Even if You Changed Internet Service Providers?

Some ISPs, especially the ones for less tech-savvy clients, will probably want you to use their supplied equipment. ISP-provided modems tend to be easy to support by the company and the connectivity is usually pre-configured. Some ISPs will allow other modems, but you would have to configure it yourself, which isn’t that hard to do.

If you want to reuse a modem you already own, verify if your ISP supports that modem model and its MAC address has not been blocked by your former Internet Provider (if it was rental equipment). If the modem is older it may not have the ability to handle speeds for which you are paying, and this bottleneck can also cause problems for others on your node.

In general, if your previous modem was supplied by a provider with a cable connection, that modem is likely a DOCSIS (Data Over Cable Service Interface Specification) modem. That modem type will not work with a DSL service provider (Digital Subscriber Line) system, and vice versa. Fiber Internet providers use fiber-optic lines and an ISP-supplied modem (Optical Network Terminal) to provide telephone, television and Internet service.

What to Do to Your Modem When Switching Providers

Whenever you are signing on to a new service or provider, they generally provide the new equipment for free (or for a very small fee incorporated into the service plan). It is usually better to use these devices since they are generally the most up-to-date, most compatible and easily serviceable when you need connection support. Often they will have a list of compatible modem model numbers, and if you already possess a compatible modem, ask customer support if they can configure it for use with their service.

If you are bringing your own compatible modem to your new provider, or BYOM, typically you’ll realize a monthly savings for not renting a modem from your new ISP.

Your new ISP may need the MAC address of the device, and if the service is the same type of internet (DSL to DSL, for example), you will need to log in and update the access information in your gateway (modem).

Most (but not all) modems from Internet Service Providers come with some basic routing functions, and as long as you are able to access the setup page of the modem, you should be able to configure both wired and wireless connectivity for your home network.

Put ISP-Supplied Modem in Bridge Mode

In some cases (and I would recommend this), the routing function of the modem can be disabled. This is usually called putting the modem in bridge mode so you can just use the modem functionality of the ISP-provided device, and use a customizable (preferably OpenWRT or DD-WRT- capable) router of your choice. Some modems allow you to configure bridge mode, while for others, the ISP will need to disable it from their end by flashing and sending a configuration file.

Change Your Router DNS

On your own router, you can change the DNS providers, whereas on an ISP-supplied modem-router, often the DNS providers are locked and the ISP can snoop on your browsing.

Modem on the left, router on the right.

Can You Use a Router That Doesn’t Come With Your ISP — Does Any Router Work With Any Internet Provider?

Normally, what most ISPs provide today is a combination modem/router. If they insist on providing you with a new modem/router, yet you have your own router, feel free to use your own router in addition to their modem. Put the modem in bridge mode to disable the router functionality, and you’re all set.

Your router can be used with any ISP. Plug your old router into one of the LAN ports on the modem supplied by your ISP, and use that for your WiFi and other wired connections. It is the modem (or modem portion of a modem-router combo) that must be compatible with the ISP.

Why would you use your own router (and a VPN)? To prevent your ISP from monitoring your internet browsing habits and selling your data.

Using Two Routers: if you want to use your old router with your new internet service, in addition to your new router:

Considerations for a modem-router combo and a second router addition:


I've been practicing OSINT and utilizing Linux as my daily operating system for over twenty years. The tools are always changing and so I'm always learning, but helping you understand the value of protecting your own data remains at the forefront of everything I do.