What is the difference between bridge network and overlay network?

Question

I have checked videos and docs related to bridge network as well as overlay network, but I just can't find the difference. Both are used to create a connection between two networks. But what is the difference? When should I use bridge and when should I use overlay network?

Answer 1

Bridge networks connect two networks while creating a single aggregate network from multiple communication networks or network segments, hence the name bridge.

In the above image Station A and Station B are connected by a bridge. Thus by using the bridge we aggregated both network in a single unit (on a high level). Bridge can even be used to create connection between networks on same host. This is generally required if the host is running multiple VM's or containers.

Overlay networks are usually used to create a virtual network between two separate hosts. Virtual, since the network is build over an existing network.

In the above image host A and host B are connected over an external network and an overlay network is built over that network. For example initially internet was built as an overlay over telephone lines, but now many telephone networks (using VoIP) are an overlay over internet.