I work at a company where I am partly responsible for IT, just because I'm semi technical and we're not big enough to warrant a dedicated role for someone else. I was asked to look into upgrading out network connection. We are looking to upgrade our work network to a fibre connection, and one of the discussions I had with the provider they mentioned the number of IP addresses we would be given. I was told that since we would be given a /30 address that we would be given two usable IP addresses. I would just like to understand, if a /30 should mean 4 working addresses, what are the other two used for? Why don't we get to use all of them?
Also, since we have other branches (3 other branches), our firm's boss told me to ask about MPLS. With MPLS, apparently we would need to have more than the /30 addresses, and they gave more technical detail that I did not understand. With the LAN hidden behind the router, why would we need more IP adresses? Why does MPLS need more IP addresses?