We have this issue as well.  MX450's acting as vpn concentrators in 1-armed mode running latest firmware.  The issue is actually the 'frames per second' table maximum of 500k is reached when scanning through to the branch locations.  When the FPS table is maxed it causes major performance degradation.  There's no solution support has provided other than to add more MXs and split up our remote auto-vpns to multiple concentrators to try and limit the impact.  We have about 150 branch locations. ... View more