I have a CRS 109, V6.20 FW3.18

If i connect my laptop to port 1 (all the other work fine) then the port goes up and down every 5 seconds.
The laptop is a dell latitude E6520 with gigabit port.
Eth1 is configured as master, 2-8 + SFP are slave

I think it has something to do with the fact that Eth1 is also a POE port.

I also had a problem configure the CRS109 with Quickset, Wisp AP mode, bridge mode, not routing, DHCP client on any interface (winbox stops working or disconnects)

can it be this ?

v6.21rc
*) fixed - master port on AR8327 switches that is put into bridge could sometimes not work properly;