Additional Information On Irb; Packet Flows Using Irb - Cisco NCS 5500 Series Configuration Manual

Integrated Routing and Bridging
show l2vpn bridge-domain detail

Additional Information on IRB

Packet Flows Using IRB

This figure shows a simplified functional diagram of an IRB implementation to describe different packet flows
between Host A, B, and C. In this example, Host C is on a network with a connection to the same router. In
reality, another router could be between Host C and the router shown.
Figure 8: IRB Packet Flows Between Hosts
When IRB is configured on a router, the following processing happens:
• ARP requests are resolved between the hosts and BVI that are part of the bridge domain.
• All packets from a host on a bridged interface go to the BVI if the destination MAC address matches
• For packets destined for a host on a routed network, the BVI forwards the packets to the routing engine
• All packets either from or destined to a host on a bridged interface go to the BVI first (unless the packet
• For packets that are destined for a host on a segment in the bridge domain that come in to the router on
the BVI MAC address. Otherwise, the packets are bridged.
before sending them out a routed interface.
is destined for a host on the bridge domain).
a routed interface, the BVI forwards the packet to the bridging engine, which forwards it through the
appropriate bridged interface.
Interface and Hardware Component Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.1.x

Additional Information on IRB

Displays the reason that a BVI is down.
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