Which of the following parameters is not mandatory for GRE configuration?

Enabling the GRE checksum is optional. A functional point-to-point GRE tunnel requires a tunnel interface, GRE as the tunnel protocol, and reachable source and destination tunnel endpoints. The source identifies the local interface or IP address used to construct the delivery header, while the destination identifies the remote GRE endpoint. Without these endpoint parameters, the device cannot correctly encapsulate and deliver packets to the peer.

The checksum field is controlled by the Checksum Present bit in the GRE header. When checksum processing is enabled, the sender includes a checksum covering the GRE header and payload, and the receiver verifies it. This can provide additional corruption detection, but it increases processing and is not required for basic GRE operation. RFC 2784 explicitly labels the checksum field as optional and states that it is present only when the Checksum Present bit is set.

Huawei SD-WAN uses GRE or GRE over IPsec to establish data channels between edge devices. The essential tunnel and transport-network information is distributed through the control system, while optional GRE functions such as checksum validation may be enabled according to operational requirements.

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