A bridge domain is one of the means by which it is possible
        to define a broadcast domain on a bridging device. It is an 
            alternative to 802.1D bridge-groups and to 802.1Q VLAN 
        Bridge domain is the service specification, and specifies the 
        broadcast domain number on which this frame of this particular
        service instance must be made available on. The physical and 
        virtual interfaces that can comprise a bridge domain are 
        heterogeneous in nature comprising Ethernet service instances,
        WAN Virtual Circuit for ATM or Frame Relay and VFIs. However,
        the frame encapsulations for all interface types are
        essentially Ethernet. 
        Without bridge-domains, VLANs would have to be globally unique
        per device and one would only be restricted to the theoretical  
             maximum of 4095 VLANs for single tagged traffic. However
        with        the introduction of bridge-domains, one can
        associate a service        instance with a bridge-domain and all
        service instances in the        same bridge-domain form a
        broadcast domain. Bridge-domain ID        determines the
        broadcast domain and the VLAN id is merely used        to match
        and map traffic. With bridge domain feature configured       
        VLAN IDs would be unique per interface only and not globally.   
            Thus bridge domains make VLAN ids have only local
        significance        per port
        Differences between Bridge Domains and 802.1AD Bridges:
        1. Scope of the VLAN technology which uses 802.1 AD is global to
        the box.
        But in case of Bridge domain, the scope of vlan is local to
        2. Switchport 802.1AD restricts the number of broadcast domain  
            on a box to 4095.
        However, with Bridge domains, we can have up to 16k broadcast   
        3. Under a single Bridge domain service instance, there can be  
                flexible service mapping criterion.(i.e match based on
        outer vlan, outer cos, inner vlan, inner cos and payload
        Whereas in case of switch port 802.1AD/dot1q this is not
        Similarities between Bridge Domains and 802.1AD Bridges:
        1. Both use the same MAC address lookup for forwarding.
        2. Both work with protocols like STP, DTP etc.
        3. Both of them classify 'ports' in a system into Bridges/Bridge
        Ethernet service instance is the instantiation of an Ethernet 
        virtual circuit on a given port on a given router. In other 
        words, an Ethernet service instance is an object that holds 
        information about the layer 2 service that is being offered
        on a given port of a given router as part of a given Ethernet
        virtual circuit. Bridge domains feature is currently supported
        on ethernet service instances only and can be later extented
        to other interfaces like ATM and Frame Relay.
        This MIB helps the network management personnel to find out the 
        details of various broadcast domains configured in the network.
        Definition of terms and acronyms:
        ATM: Asynchronous Transfer mode
        BD: Bridge Domain
        C-mac: Customer MAC
        EVC: Ethernet Virtual Circuit
        FR: Frame Relay
        SH: Split Horizon
        VFI: Virtual Forwarding Instance 
        VLAN: Virtual Local Area Network
        WAN: Wide Area Network

Imported Objects

TEXTUAL-CONVENTION, TruthValue, RowStatus, StorageTypeSNMPv2-TC
ciscoBridgeDomainMIB .
ciscoBdMIBNotifications .
ciscoBdNotificationPrefix .
ciscoBdMIBObjects .
cbdSystemInfo .
cbdMembersConfigured .
cbdMemberInfo .
cbdMemberInfoTable .
cbdMemberInfoEntry .
cbdSIIndex .
cbdMemberType .
cbdMemberOperState .
cbdMemberAdminState .
cbdMemberSplitHorizon .
cbdMemberSplitHorizonNum .
cbdMemberStorageType .
cbdMemberStatus .
cbdMembercMac .
ciscoBdMIBConformance .
ciscoBdMIBCompliances .
ciscoBdMIBGroups .