Ask the Expert

Do multiple router interfaces affect the amount of IP addresses?

Somebody told me that if a router has four interfaces (let's say four RJ-45 Jacks,) then it will have four IP addresses. Is that true? Can you please elaborate on the IP addresses of routers?

    Requires Free Membership to View

Routers usually have a variety of interfaces, including Fast Ethernet (RJ-45.) Some vendors, such as Cisco, give you the ability to add different types of interfaces depending on your needs. That way, you don't need to change your router to cover new needs.

Do you have questions about networking, VPN security or VoIP? Then visit, one of the few websites recommended by Cisco Systems in its world class Cisco Academy program.

Almost all interfaces on a router are configurable with an IP address. Some interfaces, such as the Fast Ethernet you mentioned, can be configured with one or two IP addresses. This way, you can have one physical interface configured to support two logical networks.

For example, the Fast Ethernet interface can have IP addresses and assigned to it. This means both networks ( & can 'see' the router.


This was first published in July 2008

There are Comments. Add yours.

TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Forgot Password?

No problem! Submit your e-mail address below. We'll send you an email containing your password.

Your password has been sent to: