Generally speaking, broadcast data packets cannot pass VPN tunnel.

bikerp wrote Thanks for the answer. In the meantime I found useful list of OIDs here: http://www.circitor.fr/Mibs/Mibs.php You're so great. I don't use snmp for router, but for switch. But anyway,...

Or any switch, management device? maybe the device forbids the port access.

You are using IPsec Client to Lan VPN. It's suggested upgrade into the latest firmware 180126. Never heard something like that before. You could ping your server, but you cannot connect to the RDP....

At the first place, the thing you should check is if the PC could communicate with the WAN. Uncheck Block Ping from WAN on TL-ER604W, use ping command on your PC to check if it could ping WAN IP...

need to establish another three tunnels between b, c,d.