clear ip df

Function

The clear ip df command enables fragmentation for outgoing control-plain IP packets on an interface.

The undo clear ip df command disables fragmentation for outgoing control-plain IP packets on an interface.

By default, fragmentation for outgoing control-plain IP packets on an interface is disabled.

Format

clear ip df

undo clear ip df

Parameters

None

Views

Interface view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

An IP header contains a Don't Fragment (DF) bit to identify whether packet fragmentation is allowed. Commonly, if the DF bit of a packet is set to 1, the packet cannot be fragmented. When the remote device or intermediate forwarding device receives IP packets, if it checks the packet length and discards packets whose length is longer than the Maximum Transmission Unit (MTU) on the interface, network communication is interrupted. You can run the clear ip df command to enable fragmentation for outgoing control-plane IP packets so that packets with the DF bit set to 1 are fragmented based on the MTU value on the interface.

After fragmentation for outgoing control-plain IP packets is enabled on an interface, the device sets the Don't Fragment (DF) field to 0 and fragments IP packets that meet the following conditions:

The value of the DF field in the IP packet header is 1.
The packet length is larger than the MTU value of the interface that sends the packets.

Precautions

This command takes effect only for the control-plain packets but not for the forwarding-plain packets.

Example

# Enable fragmentation for outgoing IP packets on VLANIF100.

<HUAWEI> system-view
[HUAWEI] interface vlanif 100
[HUAWEI-Vlanif100] clear ip df

# Enable fragmentation for outgoing IP packets on GE0/0/1.

<HUAWEI> system-view
[HUAWEI] interface gigabitethernet 0/0/1
[HUAWEI-GigabitEthernet0/0/1] undo portswitch
[HUAWEI-GigabitEthernet0/0/1] clear ip df