Integrated Routing and Bridging allows a Secure Firewall device operating in routed mode to contain bridge groups while also supporting routed interfaces. Multiple physical or logical interfaces can become members of one bridge group, placing them in the same Layer 2 broadcast domain, VLAN, and IP subnet. A Bridge Virtual Interface represents that bridge group at Layer 3 and functions as its gateway, permitting communication between the bridged network and routed interfaces or other bridge groups, subject to security policy. This can remove the need for an additional external Layer 2 switch when suitable firewall interfaces are available. IRB does not itself provide high availability, security-context separation, or Cisco Talos threat-intelligence updates. Those capabilities are implemented through separate features. Therefore, allowing multiple interfaces to participate in the same VLAN is the stated IRB benefit. Cisco IRB documentation

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