Message forwarding using GRE tunneling protocol

1. A method of forwarding generic routing encapsulation (GRE) encapsulated messages by a forwarding device, the method comprising:

receiving, by the forwarding device, a GRE encapsulated message from a subnet, wherein the GRE encapsulated message includes a network mask status flag and a network mask field in a GRE header, and wherein the network mask status flag is set to a first value to indicate that the network mask field contains subnet mask information of the subnet;

setting up, by the forwarding device, a tunnel table entry for the subnet based on the subnet mask information in the network mask field of the received GRE encapsulated message; and

sending, by the forwarding device, a response message to the subnet after setting up the tunnel table entry, the response message comprising information informing the subnet of the setting up of said tunnel table entry.

2. The method according to claim 1 , wherein the method comprises setting a status flag in a GRE header of the response message to indicate a presence of the subnet mask information in the GRE header before the response message is sent from the forwarding device to the subnet.

3. The method according to claim 2 , wherein the method comprises including the subnet mask information in the response message to inform the subnet of the setting up of the tunnel table entry.

4. The method according to claim 1 , wherein the method comprises setting a status flag in a GRE header of the response message to indicate the setting up of the tunnel table entry before the response message is sent from the forwarding device to the subnet.

5. The method according to claim 1 , wherein the method comprises the forwarding device updating the tunnel table entry at an expiration of a predetermined time period.

6. The method according to claim 5 , wherein the updating of the tunnel table entry is activated by a timer.

7. The method according to claim 1 , wherein the method comprises associating a tunnel destination address and the subnet mask information of the subnet in the tunnel table entry.

8. A network device for forwarding generic routing encapsulation (GRE) encapsulated packets, the network device comprising:

a processor; and

a memory storing executable instructions to cause the processor to:

receive a GRE encapsulated message from a subnet, wherein the GRE encapsulated message includes a network mask status flag and a network mask field in a GRE header, and wherein the network mask status flag is set to a first value to indicate that the network mask field contains subnet mask information of the subnet;

set up a tunnel table entry for the subnet based on the subnet mask information in the network mask field of the received GRE encapsulated message; and

send a response message to the subnet after setting up the tunnel table entry, the response message comprising information informing the subnet of the setting up of said tunnel table entry.

9. The network device according to claim 8 , wherein the processor is to set up a status flag in a GRE header of the response message to indicate a presence of the subnet mask information in the GRE header before the response message is sent to the subnet.

10. The network device according to claim 9 , wherein the processor is to include the subnet mask information in the response message to inform the subnet of the setting up of the tunnel table entry.

11. A non-transitory computer readable medium on which is stored executable instructions, which when executed by a processor, cause the processor to:

receive a GRE encapsulated message from a subnet, wherein the GRE encapsulated message includes a network mask status flag and a network mask field in a GRE header, and wherein the network mask status flag is set to a first value to indicate that the network mask field contains subnet mask information of the subnet;

set up a tunnel table entry for the subnet based on the subnet mask information in the network mask field of the received GRE encapsulated message; and

send a response message to the subnet after setting up the tunnel table entry, the response message comprising information informing the subnet of the setting up of said tunnel table entry.

12. The non-transitory computer readable medium according to claim 11 , wherein the executable instructions further cause the processor to set up a status flag in a GRE header of the response message to indicate a presence of the subnet mask information in the GRE header before the response message is sent to the subnet.