Configuring Bridge Domain Interfaces (2024)

Ethernet Virtual Circuit Overview

An Ethernet Virtual Circuit (EVC) is an end-to-end representation of a single instance of a Layer 2 service being offered by a provider to a customer. It embodies the different parameters on which the service is being offered. In the Cisco EVC Framework, the bridge domains are made up of one or more Layer 2 interfaces known as service instances. A service instance is the instantiation of an EVC on a given port on a given router. Service instance is associated with a bridge domain based on the configuration.

An incoming frame can be classified as service instance based on the following criteria:

• Single 802.1Q VLAN tag, priority-tagged, or 802.1ad VLAN tag
• Both QinQ (inner and outer) VLAN tags, or both 802.1ad S-VLAN and C-VLAN tags
• Outer 802.1p CoS bits, inner 802.1p CoS bits, or both
• Payload Ethernet type (five choices are supported: IPv4, IPv6, PPPoE-all, PPoE-discovery, and PPPoE-session)

Service instance also supports alternative mapping criteria:

• Untagged—Mapping to all the frames lacking a 802.1Q or 802.1ad header
• Default—Mapping to all the frames

For more information on the EVC architecture, see Configuring Ethernet Virtual Connections on the Cisco ASR 1000 Router chapter in the Carrier Ethernet Configuration Guide located at:

http://www.cisco.com/en/US/docs/ios-xml/ios/cether/configuration/xe-3s/ce-ether-vc-infra-xe.html

Bridge Domain Interface Encapsulation

Security Group classification includes both Source and Destination Group, which is specified by source SGT and DGT. SGT Based PBR feature provides the PBR route-map match clause for SGT/DGT based packet classification. SGT Based PBR feature supports configuration of unlimited number of tags, but it is recommended to configure the tags based on memory available in the platform.

An EVC provides the ability to employ different encapsulations on each Ethernet flow point (EFP) present in a bridge domain. A BDI egress point may not be aware of the encapsulation of an egress packet because the packet may have egressed from one or more EFPs with different encapsulations.

In a bridge domain, if all the EFPs have different encapsulations, the BDI must be untagged (using the no 802.1Q tag). Encapsulate all the traffic in the bridge domain (popped or pushed) at the EFPs. Configure rewrite at each EFP to enable encapsulation of the traffic on the bridge domain.

In a bridge domain, if all the EFPs have the same encapsulation, configure the encapsulations on the BDI using the encapsulation command. Enabling encapsulation at the BDI ensures effective pushing or popping of tags, thereby eliminating the need for configuring the rewrite command at the EFPs. For more information on configuring the encapsulations on the BDI, see the How to Configure a Bridge Domain Interface.

Assigning a MAC Address

All the bridge domain interfaces on the Cisco ASR 1000 chassis share a common MAC address. The first bridge domain interface on a bridge domain is allocated a MAC address. Thereafter, the same MAC address is assigned to all the bridge domain interfaces that are created in that bridge domain.

Note You can configure a static MAC address on a bridge domain interface using the mac-address command.

Support for IP Protocols

Brigde domain interfaces enable the Cisco ASR 1000 Series Aggregation Services Routers to act as a Layer 3 endpoint on the Layer 2 bridge domain for the following IP-related protocols:

• ARP
• DHCP
• HTTP
• ICMP
• NTP
• RARP
• SNMP
• TCP
• Telnet
• TFTP
• UDP

Support for IP Forwarding

Bridge domain interface supports the following IP forwarding features:

• IPv4 input and output access control lists (ACL)
• IPv4 input and output QoS policies. The operations supported for the input and output service policies on a bridge domain interface are:

– Classification

– Marking

– Policing

• IPv4 L3 VRFs

Packet Forwarding

A bridge domain interface provides bridging and forwarding services between the Layer 2 and Layer 3 network infrastructure.

Layer 2 to Layer 3

During a packet flow from a Layer 2 network to a Layer 3 network, if the destination MAC address of the incoming packet matches the bridge domain interface MAC address, or if the destination MAC address is a multicast address, the packet or a copy of the packet is forwarded to the bridge domain interface.

Note MAC address learning cannot not be performed on the bridge domain interface.

Note In a bridge domain, when flooding unknown unicast frames, bridge domain interface is not included.

Layer 3 to Layer 2

When a packet arrives at a Layer 3 physical interface of a router, a route lookup action is performed. If route lookup points to a bridge domain interface, then the bridge domain interface adds the layer 2 encapsulation and forwards the frame to the corresponding bridge domain. The byte counters are updated.

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.

Bridge Domain Interface Statistics

For virtual interfaces, such as the bridge domain interface, protocol counters are periodically queried from the QFP.

When packets flow from a Layer 2 bridge domain network to a Layer 3 routing network through the bridge domain interface, the packets are treated as bridge domain interface input packets and bytes. When packets arrive at a Layer 3 interface and are forwarded through the bridge domain interface to a Layer 2 bridge domain, the packets are treated as output packets and bytes, and the counters are updated accordingly.

A BDI maintains a standard set of Layer 3 packet counters as the case with all Cisco IOS interfaces. Use the show interface command to view the Layer 3 packet counters.

The convention of the counters is relative to the Layer 3 cloud, for example, input refers to the traffic entering the Layer 3 cloud from the Layer 2 BD, while output refers to the traffic leaving the Layer 3 cloud to the Layer 2 BD.

Use the show interfaces accounting command to display the statistics for the BDI status. Use the show interface <if-name> command to display the overall count of the packets and bytes that are transmitted and received.

Creating or Deleting a Bridge Domain Interface

When you define an interface or subinterface for a Cisco IOS router, you name it and specify how it is assigned an IP address.You can create a bridge domain interface before adding a bridge domain to the system, this new bridge domain interface will be activated after the associated bridge domain is configured.

Note When a bridge domain interface is created, a bridge domain is automatically created.

When both bridge domain interface and bridge domain are created, the system maintains the required associations for mapping the bridge domain-bridge domain interface pair.

The mapping of bridge domain and bridge domain interface is maintained in the system. The bridge domain interface uses the index of the associated bridge domain to show the association.

Bridge Domain Interface Scalability

Table 14-1 lists the bridge domain interface scalability numbers, based on the type of Cisco ASR 1000 Series Aggregation Services Router’s Forwarding Processors.

Table 14-1 Bridge Domain Interface Scalability Numbers Based on the Type of Cisco ASR 1000 Series Aggregation Services Router’s Forwarding Processor

How to Configure a Bridge Domain Interface

To configure a bridge domain interface, perform the following steps:

SUMMARY STEPS

1. enable

2. configure terminal

3. interface BDI interface number

4. encapsulation encapsulation dot1q <first-tag> [second-dot1q <second-tag>]

5. Do one of the following:

– ip address ip-address mask

– ipv6 address { X:X:X:X::X link-local | X:X:X:X::X / prefix [ anycast | eui-64 ] | autoconfig [ default ]}

6. mac-address { mac-address }

7. no shut

8. shut enable

DETAILED STEPS

Example

The following example shows the configuration of a bridge domain interface at IP address 2.2.2.1 255.255.255.0:

Displaying and Verifying Bridge Domain Interface Configuration

SUMMARY STEPS

1. enable

2. show interfaces bdi

3. show platform software interface fp active name

4. show platform hardware qfp active interface if-name

5. debug platform hardware qfp feature

6. platform trace runtime process forwarding-manager module

7. platform trace boottime process forwarding-manager module interfaces

DETAILED STEPS

Step 1 enable

Enables privileged EXEC mode. Enter your password if prompted.

Step 2 show interfaces bdi

Displays the configuration summary of the corresponding BDI.

Step 3 show platform software interface fp active name

Displays the bridge domain interface configuration in a Forwarding Processor.

Step 4 show platform hardware qfp active interface if-name

Displays the bridge domain interface configuration in a data path.

Router# show platform hardware qfp active interface if-name BDI4

Step 5 debug platform hardware qfp feature

Router# debug platform hardware qfp active feature l2bd client all

The selected CPP L2BD Client debugging is on.

Step 6 platform trace runtime process forwarding-manager module

Enables the Forwarding Manager Route Processor and Embedded Service Processor trace messages for the Forwarding Manager process.

Router(config)# platform trace runtime slot F0 bay 0 process forwarding-manager module interfaces level info

Step 7 platform trace boottime process forwarding-manager module interfaces

Enables the Forwarding Manager Route Processor and Embedded Service Processor trace messages for the Route Processor Forwarding Manager process during bootup.

Router(config)# platform trace boottime slot R0 bay 1 process forwarding-manager forwarding-manager level max

For additional information on the commands and the options available with each command, see the Cisco IOS Configuration Fundamentals Command Reference Guide located at:

http://www.cisco.com/en/US/docs/ios/fundamentals/command/reference/cf_book.html

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