• These interface commands are supported on a BVI:

  • arp purge-delay

  • arp timeout

  • bandwidth (The default is 10 Gbps and is used as the cost metric for routing protocols for the BVI)

  • ipv4

  • ipv6

  • mac-address

  • shutdown

• The BVI supports IP helper addressing and secondary IP addressing.

• BVI does not support MTU configuration using mtu command, which is for physical interfaces. However, ip mtu and ipv6 mtu commands, which are logical interface commands, are supported.

Like typical interface states on the router, a BVI has both an Interface and Line Protocol state.

• The BVI interface state is Up when the following occurs:

  • The BVI interface is created.

  • The bridge-domain that is configured with the routed interface bvi command has at least one available active bridge port (Attachment circuit [AC] or pseudowire [PW]).

    Note	A BVI will be moved to the Down state if all of the bridge ports (Ethernet flow points [EFPs]) associated with the bridge domain for that BVI are down. However, the BVI will remain up if at least one bridgeport is up, even if all EFPs are down.

• These characteristics determine when the the BVI line protocol state is up:

  • The bridge-domain is in Up state.

  • The BVI IP address is not in conflict with any other IP address on another active interface in the router.

The IRB/BVI implementation was originally based on single-pass or collapsed forwarding model in which each packet is processed only once. This forwarding model has some restrictions in supporting Layer 2 accounting and QoS over BVI. With this release, you have the flexibility to choose either the default single-pass model or two-pass forwarding model for packets over BVI. In the two-pass forwarding model L2 and L3 forwarding is split across two paths and packet processing happens in two cycles. This model supports Layer 2 ACL, QoS, and statistics accounting on BVI-routed packets. The earlier implementation with single-pass forwarding did not support these. You can enable the two-pass forwarding using the CLI command hw-module irb .

The two-pass forwarding model supports the following features:

• Layer 2 Access Control List (ACL)

• Layer 2 QoS on the BVI-routed packets

• Ingress statistics support for BVI in L2 to L3 packet flow

• Egress statistics support for BVI in L3 to L2 packet flow

The following table shows the configuration commands for different forwarding flows in BVI interfaces.

By default, single-pass forwarding is enabled in both IRB L2 to L3 and IRB L3 to L2 flows.

IRB Recycle Performance

The throughput of the BVI IRB recycle port is increased from 400 to 600 Gbps in native mode. The 600 Gbps throughput mode is activated using the hw-module profile qos irb-recycle-bandwidth 600 .

Router(config)#hw-module profile qos irb-recycle-bandwidth 600
  Router(config)#

Note	You should enable the two-pass forwarding capability before you configure the IRB recycle bandwidth. Before disabling the two-pass forwarding capability, you should remove the IRB recycle bandwidth configuration using the no hw-module profile qos irb-recycle-bandwidth 600 .

Router#configure terminal
Mon Mar 27 05:17:23.887 UTC
Router(config)#hw-module irb L2-L3 2-pass 
Mon Mar 27 05:17:31.421 UTC
In order to activate this new IRB model, you must manually reload the chassis/all line cards

Router#configure terminal
Mon Mar 27 05:17:43.887 UTC
Router(config)#hw-module irb L3-L2 2-pass 
Mon Mar 27 05:17:41.751 UTC
In order to activate this new IRB model, you must manually reload the chassis/all line cards
Router(config)#

Router(config)#
/*Apply ingress PM on both L2 AC and BVI interface*/
Router(config)#int fourHundredGigE 0/5/0/23.601 
Router(config-subif)#service-policy input L2AC 
Router(config-subif)#commit
Router(config-subif)#exit

Router(config)#int bvi 97
Router(config-if)#service-policy input BVI
Router(config-if)#commit
Router(config-if)#end

Router#show qos interface bvi 97 input location 0/5/CPU0 
NOTE:- Configured values are displayed within parentheses
Interface BVI97 ifh 0x20008034  -- input policy
NPU Id:                        0
Total number of classes:       2
Interface Bandwidth:           104857600 kbps
Policy Name:                   BVI
SPI Id:                        0x0
Accounting Type:               Layer2 (Include Layer 2 encapsulation and above)
------------------------------------------------------------------------------
Level1 Class                             =   DSCPAF33
New qos group                            =   3
New traffic class                        =   2

Policer Bucket ID                        =   0x21
Policer Stats Handle                     =   0x0
Policer committed rate                   =   150390 kbps (150 mbits/sec)
Policer peak rate                        =   200195 kbps (200 mbits/sec)
Policer conform burst                    =   186624 bytes (default)
Policer exceed burst                     =   436096 bytes (default)

Level1 Class                             =   class-default

Default Policer Bucket ID                =   0x20
Default Policer Stats Handle             =   0x0
Policer not configured for this class

Interface BVI97 ifh 0x20008034  -- input policy
NPU Id:                        1
Total number of classes:       2
Interface Bandwidth:           104857600 kbps
Policy Name:                   BVI
SPI Id:                        0x0
Accounting Type:               Layer2 (Include Layer 2 encapsulation and above)
------------------------------------------------------------------------------
Level1 Class                             =   DSCPAF33
New qos group                            =   3
New traffic class                        =   2

Policer Bucket ID                        =   0x21
Policer Stats Handle                     =   0x0
Policer committed rate                   =   150390 kbps (150 mbits/sec)
Policer peak rate                        =   200195 kbps (200 mbits/sec)
Policer conform burst                    =   186624 bytes (default)
Policer exceed burst                     =   436096 bytes (default)

Level1 Class                             =   class-default

Default Policer Bucket ID                =   0x20
Default Policer Stats Handle             =   0x0
Policer not configured for this class

Router#show qos int fourHundredGigE 0/5/0/23.601 input 
NOTE:- Configured values are displayed within parentheses
Interface FourHundredGigE0/5/0/23.601 ifh 0xa00883a  -- input policy
NPU Id:                        1
Total number of classes:       2
Interface Bandwidth:           400000000 kbps
Policy Name:                   L2AC
SPI Id:                        0x0
Accounting Type:               Layer2 (Include Layer 2 encapsulation and above)
------------------------------------------------------------------------------
Level1 Class                             =   DSCPAF43
New qos group                            =   2
New traffic class                        =   1

Policer Bucket ID                        =   0x9
Policer Stats Handle                     =   0x0
Policer committed rate                   =   99609 kbps (100 mbits/sec)
Policer conform burst                    =   124672 bytes (default)

Level1 Class                             =   class-default

Default Policer Bucket ID                =   0x8
Default Policer Stats Handle             =   0x0
Policer not configured for this class
Router#

You must be in a user group associated with a task group that includes the proper task IDs. The command reference guides include the task IDs required for each command. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Before configuring IRB, be sure that these tasks and conditions are met:

• Know the IP addressing and other Layer 3 information to be configured on the bridge virtual interface (BVI).

• Complete MAC address planning if you decide to override the common global MAC address for all BVIs.

• Be sure that the BVI network address is being advertised by running static or dynamic routing on the BVI interface.

Before configuring IRB, consider these restrictions:

• Only one BVI can be configured in any bridge domain.

• The same BVI can not be configured in multiple bridge domains.

• MTU configuration and fragmentation of packets is not supported on BVI interfaces.

• The following areas are not supported on the BVI:

  • Access Control Lists (ACLs). However, Layer 2 ACLs can be configured on each Layer 2 port of the bridge domain.

  • IP fast reroute (FRR)

  • TI-LFA

  • SR

  • LDP

  • NetFlow

  • MoFRR

  • Quality of Service (QoS)

  • Traffic mirroring

  • Unnumbered interface for BVI

  • Video monitoring (Vidmon)

  • IRB with 802.1ah (BVI and Provider Backbone Bridge (PBB) should not be configured in the same bridge domain).

  • PIM snooping. (Need to use selective flood.)

  • VRF-aware DHCP relay

• The following areas are not supported on the Layer2 bridging (with BVI):

  • Static mac entry configuration in Bridge.

  • Mac ageing configuration at global config mode.

  • MAC Learning Disable.

  • Vlan rewrite.

• QOS configuration on BVI interface is not supported for egress.

• Label allocation mode per-CE with BVI is not supported in an access network along with PE-CE protocols enabled.

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.

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 the BVI MAC address. Otherwise, the packets are bridged.

• For packets destined for a host on a routed network, the BVI forwards the packets to the routing engine before sending them out a routed interface.

• All packets either from or destined to a host on a bridged interface go to the BVI first (unless the packet is destined for a host on the bridge domain).

• For packets that are destined for a host on a segment in the bridge domain that come in to the router on a routed interface, the BVI forwards the packet to the bridging engine, which forwards it through the appropriate bridged interface.