It has something to do with the VLAN tagging of 1. I can reproduce the problem with the connection to the ER7206. If I turn on tagging of VLAN 1 then I can no longer ping the printer from anywhere...

I have an old TL-SG3424P V2 with latest available firmware. I have two VLANs (1 for management and 13 for guest traffic). Mostly everything works. Access Points are connected and setup to tag the...