I see that you have all the ports on the SR520 set to trunking mode. If you don't want to trunk VLANs between the switch and the SR520, just set the ports to access mode using CCA (this it the Desktop Smart Port mode).
If you do want to trunk VLANs (and route between them on the SR520), then you will have to have matching VLAN IDs on either side - as you mention, you are using VLAN80 natively on the SR520.
By default the switch uses VLAN 1 I believe, so as this VLAN already exists on your SR520, you could just add an IP address (from a new subnet) to that VLAN interface and communicate with the switch that way.
Hello, This article will describe how to configure PPTP VPN on the new
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