Can a router have more than one IP address? Will each of its interfaces have a different IP address?

Yes, a router can have more than one IP address, and this is a fundamental aspect of how routers operate.

Multiple IP Addresses on a Router

A typical home or business router has at least two IP addresses, each associated with a different interface:

1. WAN (Wide Area Network) Interface: This interface faces the internet and is assigned a public IP address by the ISP. This is often a dynamic IP address, but it can be static depending on the ISP's configuration15.

2. LAN (Local Area Network) Interface: This interface faces the local network and is assigned a private IP address. Common examples include addresses like 192.168.1.1, 10.1.10.1, or similar private IP address ranges15.

Multiple Interfaces with Different IP Addresses

In general, each layer-3 interface on a router must have a unique IP address. It is not possible to assign the same IP address to two or more layer-3 interfaces on the same router4.

However, there are some advanced configurations where a router can use a single IP address across multiple interfaces, but these involve specific techniques such as:

• IP Unnumbered: This method allows an interface to borrow the IP address of another interface, typically a loopback interface. This is useful in certain network configurations but does not mean the interfaces have the same IP address in the traditional sense4.

• VRFs (Virtual Routing and Forwarding): These can be used to create separate routing tables, allowing different interfaces to use the same IP address space but within different virtual routing contexts4.

In standard configurations, each interface on a router will have its own unique IP address to ensure proper routing and network functionality.