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
The WAN interface needed would depend on the WAN media. Yours is Ethernet?
If so, what you might consider is trunking your built-in Ethernet ports to a VLAN capable switch. Although the 2851 comes with gigE interfaces, it doesn't have gigE perforamance capacity. (On that, whether your 2851 can deal with 20 Mbps, depends on is the 20 Mbps the total aggregate for all traffic? If so, the answer should be yes.)
