global-gre forward-mode

Function

The global-gre forward-mode command configures the forwarding mode for all distributed GRE tunnels.

The undo global-gre forward-mode command cancels the configuration.

By default, the forwarding mode of distributed GRE tunnels is through.

Format

global-gre forward-mode { through | loopback }

undo global-gre forward-mode

Parameters

Parameter	Description	Value
through	Indicates that the forwarding mode of distributed GRE tunnels is software loopback, which is also called the high-performance forwarding mode.	-
loopback	Indicates that the forwarding mode of distributed GRE tunnels is hardware loopback, which is also called the low-performance forwarding mode.	-

Parameter

Description

Value

through

Indicates that the forwarding mode of distributed GRE tunnels is software loopback, which is also called the high-performance forwarding mode.

loopback

Indicates that the forwarding mode of distributed GRE tunnels is hardware loopback, which is also called the low-performance forwarding mode.

Views

System view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
forwarding	write

Usage Guidelines

Usage Scenario

Distributed GRE tunnels on the

Router support two forwarding modes: through and loopback. By default, the forwarding mode of distributed GRE tunnels is through.

In through mode, the device boasts high forwarding performance but does not allow for downstream HQoS implementations.
In loopback mode, the device provides lower forwarding performance but allows for downstream HQoS implementations.
You can configure a proper forwarding mode based on service requirements. If the traffic rate on the GRE tunnel interface is lower than half of the board bandwidth, configuring the forwarding mode as loopback is recommended.

Precautions

The global-gre forward-mode command takes effect for distributed GRE tunnels only.

Distributed GRE tunnels can work in either software loopback or hardware loopback mode. When working in software loopback mode, a GRE interface has a bandwidth equal to the maximum bandwidth supported by the interface board. When working in hardware loopback mode, a GRE interface has a bandwidth half of that supported by the interface board. If high forwarding performance is required, using the software loopback mode is recommended.

In VPLS over distributed GRE tunnel scenarios, removing a board may cause packet loss or redundancy in the broadcast, multicast, or unknown unicast services of some VSIs.

In VS mode, this command is supported only by the admin VS.

Example

# Configure the forwarding mode of distributed GRE tunnels as loopback.

<HUAWEI> system-view
[~HUAWEI] global-gre forward-mode loopback