D-Link DFL-260E User Manual page 449

9.7.6. Specific Symptoms
Chapter 9. VPN
By using ikesnoop when both sides initiate the tunnel, it should be simple to compare the network
that both sides are sending in phase-2. With that information it should be possible to spot the
network problem. It can be the case that it is a network size mismatch or that it does not match at all.
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