Check router for VPN Throughput - L2TP VPN

Question

I am working on setting up a VPN for our office.   I have the PPTP version working but am unable to get L2TP to function.  Through various testing methods (setting up our Mac Yosemite server as a VPN and testing it in and out of the office), I am leaning towards an issue with the router not allowing some of the protocols required by an L2TP through.  The reason being I am able to create a L2TP VPN connection with my Mac server when using the internal IP address, but not when using the outside IP address (which to me means the signal is being blocked at the router.)
The server is receiving the SCCRQ from the client and trying to send the SCCRP which the client is not receiving when trying to connect from outside the office.
I have checked all the ports required and they are open (show ip ports), but can not figure out how to check for ESP Protocol 50?  Does anyone know how to check this protocol?  And if this isn't the solution, does any have other methods I can use to find the issue?
Thank you,
Chris

Answer 1

I think 2811 can handle this task
2811 supports up to 1500 VPN tunnels with the AIM-EPII-PLUS Module
http://www.cisco.com/en/US/products/ps5881/index.html
So no problem with 165 VPNs...
If you speaking about huge traffic volume - you should focus on speed of Internet connectivity in head office - If you have 10 Mbit line for head office you get only 60Kbit per tunnel (10Mbit/165)
M.
Hope that helps rate if it does