The ping operation is successful but services are unavailable on the AR configured with GRE over IPSec

IPSec encapsulates IP packets. As a result, the IP packet length becomes longer. If the IP packet length exceeds the MTU during transmission, the IP packets are fragmented and sent. The receiver needs to reassemble and parse the fragments. Fragmentation and reassembly consume CPU resources, and encryption and decryption of fragments also consume many CPU resources. When there are many fragments, CPU resources may be insufficient. In this case, the access is slow and packets are discarded.
If small-sized ping packets can be transmitted but large-sized ping packets cannot be transmitted, check the MTU of the ISP. If the MTU of the ISP cannot be confirmed, perform the ping operation with different bytes to determine the intermediate MTU. Then change the MTU on the device.

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