Thanks for the suggestions.

It will be a week or so before I can "mess about" with a system that is basically working.

I'll come back once I've been able to experiment further.

I've now been able to try the service provider's (rather basic) Linksys. 945Mb/s download (so as expected with a 1Gb/s interface).

> ppa -x

WAN1 status : Enable
WAN1 phy_type : ETHERNET
WAN1 session check = hw_acc_general
WAN2 status : Enable
WAN2 phy_type : ETHERNET
WAN2 session check = hw_acc_general
WAN3 status : Disable
WAN3 phy_type : WIRELESS
WAN3 session check = NULL
WAN4 status : Disable
WAN4 phy_type : WIRELESS
WAN4 session check = NULL
WAN5 status : Enable
WAN5 phy_type : USB
WAN5 session check = NULL

A quite respectable 733Mb/s with hardware accelleration off (or 685Mb/s with it on) so perhaps I'll leave it at that for now.

I'm sure that it will be something about my (fairly simple) configuration that stops it working but I can't see what.

Thanks for all the help.

Do check this chart out though, for the conditions needed to enable 'Hardware Acceleration' on specific models of router:

https://www.draytek.co.uk/support/guides/kb-hardware-acceleration-tips

Thanks for the suggestion.

I may have got somewhere with this.

I have 2 WANs and a Load-Balance/Route Policy so that certain clients go out of a given WAN. There are 9 rules in the table. My test PC was set to go out of the 1Gb/s connection.

Turning the relevant Load-Balance/Route Policies off has given me an 840Mb/s speed test result and shows accelerated sessions.

> ppa -v

%PPA is enabled
%PPA NAT is enabled
% PPA mode is Manual (traffic)
%PPA Protocol TCP 1, UDP 1
%PPA WLAN to LAN is disabled
%PPA WLAN to WAN is disabled
%PPA Multicast is enabled
%PPA IPSec is enabled
%PPA IPSec Protocol TCP enabled
%PPA IPSec Protocol UDP enabled
%PPA two way enable
%PPA time is 10
%PPA range is 8000
%PAE range is 2048
%MPE range is 5952
%PPA LAN entries 8, working 2
%PPA WAN entries 8, working 2
%PPA statistics interval: 5 sec
>

The disadvantage is that with load balancing off there is a tendancy to pick the (slower) WAN1 for speed tests (and I guess general connections) so I won't be leaving it like that but at least I've found that Load-Balance seems to disable the hardware acceleration.

The one remaining puzzle is not quite making the 945Mb/s seen with the Linksys but the practical impact is only on speed tests.

VIP - ensure your have Data Flow Monitor (under Diagnostics) disabled!

Shouldn't matter on a 2927 (or 2865/2866) - read HodgesanDY's link above...