Two VPN's causing router crash problem.

Hi,

This is the setup we have


( Internet )
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WAN interface
[Main router]
LAN port - x.x.x.238
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WAN port x.x.x.233 WAN port
x.x.x.234
[Subnet 1 VPN router] [Subnet
2 VPN router]
LAN port set to 192.168.1.0/24 LAN port set
to 192.168.2.0/24
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-----------------
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Hopefully that looks alright!

Basically there are 5 usable addresses assigned by the ISP - the
initial ADSL router picks up its WAN address via DHCP and this is a
variable address and can change with a new lease.

There is a subnet set up between the three routers using the subnet
supplied by the ISP.

This means that the two subnet routers are accessible to the internet
using their IP addresses - and this is what is needed to get VPN's
working. These IP addresses are two of the five usable addresses from
the ISP.

The problem we seem to have is that when both VPN's are used
simultaneously the main router - an Allied Telesyn AT-AR256E - seems to
crash. When only a single VPN is being used we're fine.

Any thoughts, ideas, pointers etc would be gratefully received.

Kevin