ipsec df-bit

Use ipsec df-bit to configure the DF bit for the outer IP header of IPsec packets on an interface.

Use undo ipsec df-bit to restore the default.

Syntax

ipsec df-bit { clear | copy | set }

undo ipsec df-bit

Default

The DF bit is not configured for the outer IP header of IPsec packets on an interface. The global DF bit setting is used.

Views

Interface view

Predefined user roles

network-admin

mdc-admin

Parameters

clear: Clears the DF bit in the outer IP header. IPsec packets can be fragmented.

copy: Copies the DF bit setting of the original IP header to the outer IP header.

set: Sets the DF bit in the outer IP header. IPsec packets cannot be fragmented.

Usage guidelines

This command is effective only when the IPsec encapsulation mode is tunnel mode. It is not effective in transport mode because the outer IP header is not added in transport mode.

This command does not change the DF bit for the original IP header of IPsec packets.

If multiple interfaces use an IPsec policy that is bound to a source interface, you must use the same DF bit setting on these interfaces.

Packet fragmentation and reassembly might cause packet forwarding to be delayed. You can set the DF bit to avoid the forwarding delay. However, to prevent the IPsec packets from being discarded, you must make sure the path MTU is larger than the IPsec packet size. As a best practice, clear the DF bit if you cannot make sure the path MTU is larger than the IPsec packet size.

Examples

# Set the DF bit in the outer IP header of IPsec packets on Vlan-interface100.

<Sysname> system-view
[Sysname] interface vlan-interface 100
[Sysname–Vlan-interface100] ipsec df-bit set

Related commands

ipsec global-df-bit