What is the purpose of a bridge in RouterOS, and which commands create a bridge including two interfaces?

• A. A bridge creates a single Layer 2 domain; create with /interface bridge add name=bridge1 and add ports with /interface bridge port add bridge=bridge1 interface=ether1 and /interface bridge port add bridge=bridge1 interface=ether2
• B. A bridge creates a single Layer 2 domain; create with /interface bridge add name=bridge1 and add ports with /interface bridge port add bridge=bridge1 interface=ether1 and /interface bridge port add bridge=bridge1 interface=ether2
• C. A bridge separates Layer 2 domains into distinct VLANs.
• D. A bridge is used to NAT traffic between interfaces.

Answer: (B)

A bridge in RouterOS creates a single Layer 2 domain, effectively turning the connected interfaces into one little switch. When interfaces are members of the same bridge, frames can be forwarded between them at Layer 2, and devices on either side learn MAC addresses the same way they would on a physical switch. This lets hosts on ether1 and ether2 communicate directly without routing.

To set this up, you first create the bridge and then attach the two interfaces to it. The correct commands are: create the bridge with /interface bridge add name=bridge1, then add the ports with /interface bridge port add bridge=bridge1 interface=ether1 and /interface bridge port add bridge=bridge1 interface=ether2. After that, both Ethernet ports are part of the same broadcast domain.

This is different from separating Layer 2 domains or using NAT. A bridge itself doesn’t split into VLANs or perform NAT; bridging combines ports into one L2 domain, while VLANs would require additional tagging and configuration, and NAT operates at Layer 3.