Does the Mikrotik hEX (RB750gr3) support half bridge mode? I have a Fortigate firewall that I'd like to continue using, but it gets hammered on PPPoE with CPU going through the roof, limiting bandwidth. I'd like the Mikrotik to sit in front and act as a half bridge, with public IP on the firewall but the Mikrotik doing the PPPoE encapsulation. Is this 1. possible and if so 2. supported?

Anyone?

Mikrotik RouterOS does not have PPPoE Relay (half bridge) feature, yet. So you cant run your mikrotik router in half bridge mode.

But IF you have a modem/gateway that supports PPPoE Relay (aka Half Bridge or Passthrough), then you can use PPPoE client on routerOS to connect PPPoE server via modem/gateway's relay.

Normally you need two static IPs for Half bridge. Modem/gateway does NAT with first IP, and another client gets second static IP via PPPoE relay. But you can set dummy user/password and disable NAT on modem/gateway and use single static IP address via relay on your Mikrotik router. Of course you would need modem/gateway with PPPoE relay feature.

the solution is to terminate PPPoE on firewall and drop all incoming packets from PPPoE if they dont participate in NAT by writing a rule. of course, if it allows you to do so.

If it is not possible, simply replace the firewall as it should be piece of junk. Many of new ones can terminate 100 mbps PPPoE with %0-1 load.