Currently, at my business I have:
Cable Modem (Charter Internet)
Cisco Router (Supplied and managed by outside company)
Computers and printers (all hardwired)
The network consists of 3 company computers and 2 company printers. There are also 2 "personal" computers on the network. Those personal computers tend to be very slow when connecting to the internet. Plugging a computer directly into the modem fixes the speed problem.
The router is managed by a third party. I need to request changes to the router, which often requires pulling teeth. I asked a few years back to open a port on the router for remote viewing of the security cameras, and after hours of "TELLING" them to do it, it took them 30 minutes over a dial-up modem to open the port. The reason I was told was because the Cisco router is old and doesn't have a GUI, so it's all coding.
What I want to do is add "something" between the modem and the Cisco router. The only issue is I don't know what ports would need to be open for the network to work properly. Another idea was a switch after the modem, to them split to the company Cisco and to a "personal" router. However, I'm pretty sure Charter won't allow multiple IP addresses after the modem.
Any suggestions or help would be greatly appreciated.
In your current setup the Cisco is probably acting as a DHCP server, so adding another one before the Cisco will not do. You can probably add a switch between the modem and Cisco router but any device you connect to the switch will need to have its TCP/IP addresses (IP, Subnet, Gatway and DNSs) manually added.