Configuring Layer 3 Communication Between VBDIF Interfaces

VBDIF interfaces are Layer 3 logical interfaces. After creating VBDIF interfaces, you can configure Layer 3 features on these interfaces.

Usage Scenario

When EVC that defines Layer 2 interfaces without IP addresses is used to communicate with a Layer 3 network, VBDIF interfaces that are logical interfaces in a bridge domain can be configured. VBDIF interfaces are network layer interfaces and can be assigned IP addresses. These VBDIF interfaces with IP addresses assigned can communicate with the Layer 3 network through the EVC module.

Both Layer 2 and Layer 3 traffic is transmitted over the VBDIF interface. Running the shutdown command in the VBDIF interface view prohibits only Layer 3 traffic. After running the display interface vbdif command, you can view that traffic statistics still increase on this VBDIF interface.

To prohibit all traffic on the VBDIF interface, run the shutdown command in the BD view.

Pre-configuration Tasks

Before configuring Layer 3 communication between VBDIF interfaces, complete the following task:

Establishing the EVC Model

Configure the rewrite pop { single | double } command as an action to have all VLAN tags removed from packets.

Procedure

Run system-view
The system view is displayed.
Run interface vbdif bd-id
A VBDIF interface is created, and the VBDIF interface view is displayed.

The VBDIF interface number must be the ID of a BD that has been created.

If an interface is bound to a BD, a VBDIF interface can be created for the BD only when the interface has EVC Layer 2 sub-interfaces encapsulated with untag, dot1q, QinQ.
Run ip address ip-address { mask | mask-length } [ sub ]
An IP address is assigned to the VBDIF interface for communication at the network layer.

If IP addresses assigned to VBDIF interfaces belong to different network segments, a routing protocol must be configured to provide reachable routes. Otherwise, VBDIF interfaces cannot communicate with each other at the network layer. For configurations of routing protocols, see the NetEngine 8000 F Configuration Guide - IP Routing.
(Optional) Run mtu mtu
The maximum transmission unit (MTU) is configured for the VBDIF interface.

Generally, the IP layer controls the maximum length of frames that are sent each time. Any time the IP layer receives an IP packet to be sent, it checks which local interface the packet needs to be sent to and queries the MTU of the interface. Then, the IP layer compares the MTU with the length of the packets to be sent. If the packet length is greater than the MTU, the IP layer fragments the packet to ensure that the length of each fragment is smaller or equal to the MTU.

If forcible unfragmentation is configured, certain packets are lost during data transmission at the IP layer. To ensure jumbo packets are not dropped during transmission, you need to configure forcible fragmentation. In this case, you can run the mtu command to set the size of a fragment.

After using the mtu command to change the MTU of a VBDIF interface, you need to change the MTU of the peer VBDIF interface to ensure that the MTUs of both interfaces are the same. Otherwise, services may be interrupted.
(Optional) Run bandwidthbandwidth
The bandwidth is configured for the VBDIF interface.

The bandwidth command mainly ensures that the network management station (NMS) can acquire the bandwidth of the VBDIF interface.
(Optional) Run forward-mode loopback
Set the packet forwarding mode on a VBDIF interface to loopback.

After the forward-mode loopback command is run to set the packet forwarding mode to loopback, downstream MTU fragmentation is supported on a VBDIF interface and multicast traffic statistics are for a copy of the traffic forwarded from VBDIF interfaces.
(Optional) Run damping time delay-time
The BD damping function is enabled, and the delay after which the BD Down event is reported to the BDIF interface is set.

If all the interfaces added to a BD go Down, the BD will report a BD Down event to the corresponding BDIF interface, causing the BDIF interface status to change. The master/slave switchover will cause the BDIF interface to alternate frequently between Up and Down. As a result, network flapping occurs. To avoid this situation, enable the BD damping function on the BDIF interface. If the last Up interface in the BD becomes Down, the device enabled with the BD damping function will report the BD status to the BDIF interface after the set delay expires. If an interface in the BD becomes Up before the set delay expires, the BDIF interface status remains Up.
Run commit
The configuration is committed.

Verifying the Configuration

After configuring a VBDIF interface, run the display interface vbdif command. The command output shows the physical status, link protocol status, IP address, and mask of a VBDIF interface.