How to Discover Core Router Brand

Quick answer is it depends….

Long answer is it will depend on your service provider or manager of the device you are trying to gather information on. Also it will depend on how they expect you to interact with the device. If you are a simple end of the line consumer then as Keller mentioned most ISPs will limit the amount of identifying information available to an end user, leaving only fingerprinting as a valid way to determine the device type (nmap).

Also ISPs have been known to put useful information in the reverse dns entries of the ip address hops of you connections. Often you can gather not only device manufacture, but model number and which interface you traffic is traversing (Time Warner used to do this, haven’t checked to see if they still are).

Where as if you have a legitimate need for the information, then the answer is just ask them, most ISP will gladly share the information if you are up front and honest with the reasons why you need that information. For example if you are peering with that ISP or have noticed “interesting” behavior when your traffic crosses their device. They would like to hear about it.

Now if you are asking how to technically finger print a device across the internet that you have no direct interaction with, then that is a post for a security group and they can explain tcp fingerprinting and all the gory details.