Cisco ASR1006 Configuration Guide - Page 365

Configuring Bridge Domain Interfaces Information About Bridge Domain Interfaces During a Layer 2 lookup on a bridge domain to which the bridge domain interface belongs, the bridge domain forwards the packets to the correct service instance based on the destination MAC address. Link States of a Bridge Domain and a Bridge Domain Interface Bridge domain interface acts as a routable IOS interface on Layer 3 and as a port on a bridge domain. Both bridge domain interfaces and bridge domains operate with individual administrative states. Shutting down a bridge domain interface stops the Layer 3 data service, but does not override or impact the state of the associated bridge domain. Shutting down a bridge domain stops Layer 2 forwarding across all the associated members including service instances and bridge domain interfaces. The operational state of a bridge domain is influenced by associated service instances. Bridge domain interface cannot be operational unless one of the associated service instance is up. Note Because a bridge domain interface is an internal interface, the operational state of bridge domain interface does not affect the bridge domain operational state. BDI Initial State The initial administrative state of a BDI depends on how the BDI is created. When a BDI is created at boot time in the startup configuration, the default administrative state for the BDI will be up, and will remain in this state unless the startup configuration includes the shutdown command. This behavior is consistent with all the other interfaces. When a BDI is created dynamically by a user at command prompt, the default administrative state is down. BDI Link State As with all Cisco IOS interfaces, a BDI maintains a link state that comprises of three states, administratively down, operationally down, and up. The link state of a BDI is derived from two independent inputs, the BDI administrative state set by the corresponding users and the fault indication state from the lower levels of the interface states. defines a BDI link state based on the state of the two inputs. Fault Indication State - No faults asserted At least one fault asserted BDI Administrative State Shutdown Admin-down Admin-down No Shutdown Up Operationally-down Bridge Domain Interface Statistics For virtual interfaces, such as the bridge domain interface, protocol counters are periodically queried from the QFP. Cisco ASR 1000 Series Aggregation Services Routers Software Configuration Guide 5