Disclaimer
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
Liability Disclaimer
In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Posting
I agree with Leo, as far as I know there's not typical or standard size for a "Medium ISP". Sizing is dictated mainly by amount of traffic the device will need to deal with. Additionally, you need to consider the number and kind of interfaces. Also for an ISP BGP usage, likely the device will need to deal with full Internet BGP tables, but there could be multiple BGP peers.
