Actually I use Mikrotik in my entire network. We are an ISP, around 3k customers.
I need to solve the following scenario: Put two IP addresses in the same routerboard (public addresses) in transparent mode, so the RB would work as an "Transparent Filter".
One port would be the WAN side (same gateway, but two public addresses passing by) and I would use two separate ports in customer side. This is really necessary, because we use ubiquiti equipment in Bridge mode to do the P2P wireless links and our network is entirely bridged (no vlan, no routed network, nothing, everyone can see each other in a huge bridge).
So I need to "filter" only packets from gateway to customer, and from customer to gateway. So the customer will not see any broadcast from my network, and my network will not see any broadcast from customer LAN. Even if he uses an IP address from other customer (outside WAN) it will not cause any trouble in my environment. So the schema is as following (RB750GL):
ether1 - WAN PORT (can see gateway with x.x.x.254/24)
ether2 - Customer network 1 (one public address here x.x.x.2/24)
ether3 - Customer network 2 (other public address here x.x.x.3/24)
ether4 - Free
ether5 - Free
So the RB will work as an bridge-firewall equipment, filtering broadcast from "Wan side" to "customer side" and vice versa. This is really necessary, because we're using public addresses in our customers, but with few free public addresses in our ASN (so its not good to use a public address in RB and use RB as ROUTER with firewall enabled)...
Any help would be very appreciated
Regards!
Artur Portella.