Hi all... I have 2820n's at 2 sites. Both have reliable ADSL connections with approx 6mb down/0.5mb up. I have a LAN to LAN PPTP VPN setup between the sites which all works fine in normal daily operation. Sometimes i find the VPN drops connection, is down for about a min, then reconnects. This causes users at one of the sites a real problem with application timeouts. This VPN dropout seems to coincide with periods of heavy downloading at the other site.

Is there a way to reserve bandwidth for the VPN tunnel such that even if general downloads are high, the VPN will retain say 0.5mb of the bandwidth? Can i use QoS for that?

QoS works for Lan2Lan connections.
I never tried with dial-in connections, but, Lan2Lan definitely yes.

in one of the QoS Classes, make a rule like:
local address: 192.168.0.0/16, remote: 192.168.0.0/16 and assign this a useful percentage of bandwidth.
Then all traffic from private subnets to or from private subnets will be guaranteed a minimum bandwidth.
Maybe make a class which only contains this rule, because otherwise when bandwidth is saturated other services in the same class will again fight with the VPN traffic for the remaining bandwidth.
Also consider using an IPSec tunnel instead of PPtP. I dont care if this is safer or not, but, it is more transparent and, whenever I used PPtP I had more hangs when I copied large files with PPtP then with an IPSec tunnel.

you can watch of the QoS is working correct in the "online statistics" under setup under the Quality of service menu.

Thanks nobody - appreciate the reply. Will try this and will report back with settings if i get it working in case its useful for others