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CLI-based Configuration Guide - VPN

AR100, AR120, AR150, AR160, AR200, AR1200, AR2200, AR3200, and AR3600 V200R010

This document describes VPN features on the device and provides configuration procedures and configuration examples.
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(Optional) Configuring the DF Flag Bit for GRE Packets

(Optional) Configuring the DF Flag Bit for GRE Packets


The length of GRE-encapsulated packets may exceed the maximum transmission unit (MTU) of the outbound interface on the local device. If the remote device on a GRE tunnel does not support fragmentation and reassembly, it cannot decapsulate packets and will discard or invalidly process packets, affecting packet transmission.

To prevent packet loss, you can set the DF flag bit for GRE packets to clear to allow fragmentation of GRE packets. After the DF flag bit is set to clear, the local device pre-calculates the packet length. If the packet length after GRE encapsulation exceeds the MTU, the local device fragments the GRE packets and encapsulates each fragment. After packets reach the GRE remote device, the remote device can decapsulate the fragments without having to reassemble them. The decapsulated packets will be forwarded normally.


  1. Run system-view

    The system view is displayed.

  2. Run gre df-bit { clear | set | copy }

    The DF flag bit is set for GRE packets.

    By default, the DF flag bit for GRE packets uses the clear mode.

Updated: 2019-08-07

Document ID: EDOC1100033725

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