How Many Broadcast Domains Are Present on a Router?

C

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To determine the number of broadcast domains on a router with four interfaces, where each interface is connected to four switches, we need to understand the concept of broadcast domains and how they are affected by network devices like routers and switches.

A broadcast domain is a logical division of a computer network where all devices within the domain can directly send broadcast messages to each other. Broadcast messages are packets that are sent to all devices on a network segment. Routers, by default, do not forward broadcast messages between different interfaces, while switches do forward broadcast messages to all devices connected to them.

In this scenario, we have four interfaces on the router, and each interface is connected to four switches. Let's analyze the impact of switches and routers on the broadcast domains:

1. Switches: Each switch, being a layer 2 device, creates its own broadcast domain. This means that all devices connected to a switch can communicate directly using broadcast messages. Since each interface on the router is connected to a separate switch, we have a total of four switches. Therefore, we have four broadcast domains created by the switches.

2. Router: Routers, being a layer 3 device, do not forward broadcast messages between different interfaces by default. Each interface on the router represents a separate network segment or subnet. Since we have four interfaces on the router, each connected to a separate switch, we have four network segments/subnets.

However, we need to consider that a router can also be configured with VLANs (Virtual Local Area Networks) to create logical broadcast domains. If the switches are configured with VLANs and the router is configured with VLAN interfaces, then each VLAN would represent a separate broadcast domain. But based on the information provided in the question, it does not mention VLAN configurations.

Therefore, considering the default behavior of routers without VLANs, the number of broadcast domains on the router would be the same as the number of network segments/subnets, which is four. Hence, the correct answer would be:

C. 4