Adding and Editing GRE Tunnel

1. If creating a new GRE configuration, assign it a name to distinguish its configuration.
2. Define the following GRE tunnel settings:

   DSCP Options	Use the spinner control to set the tunnel DSCP / 802.1q priority value from encapsulated packets to the outer packet IPv4 header.
   Tunneled VLANs	Define the VLAN connected clients use to route GRE tunneled traffic within their respective WLANs.
   Native VLAN	Set a numerical VLAN ID (1 - 4094) for the native VLAN. The native VLAN allows an Ethernet device to associate untagged frames to a VLAN when no 802.1Q frame is included in the frame. Additionally, the native VLAN is the VLAN untagged traffic is directed over when using a port in trunk mode.
   Tag Native VLAN	Select this option to tag the native VLAN. The IEEE 802.1Q specification is supported for tagging frames and coordinating VLANs between devices. IEEE 802.1Q adds four bytes to each frame identifying the VLAN ID for upstream devices that the frame belongs. If the upstream Ethernet device does not support IEEE 802.1Q tagging, it does not interpret the tagged frames. When VLAN tagging is required between devices, both devices must support tagging and be configured to accept tagged VLANs. When a frame is tagged, the 12 bit frame VLAN ID is added to the 802.1Q header so upstream Ethernet devices know which VLAN ID the frame belongs to. The device reads the 12 bit VLAN ID and forwards the frame to the appropriate VLAN. When a frame is received with no 802.1Q header, the upstream device classifies the frame using the default or native VLAN assigned to the Trunk port. The native VLAN allows an Ethernet device to associate untagged frames to a VLAN when no 802.1Q frame is included in the frame. This feature is disabled by default.
   MTU	Set an IPv4 tunnel‘s maximum transmission unit (MTU) from 128 - 1,476. The MTU is the largest physical packet size (in bytes) transmittable within the tunnel. Any messages larger than the MTU are divided into smaller packets before being sent. A larger MTU provides greater efficiency because each packet carries more user data while protocol overheads, such as headers or underlying per-packet delays, remain fixed; the resulting higher efficiency means a slight improvement in bulk protocol throughput. A larger MTU results in the processing of fewer packets for the same amount of data. For IPv4, the overhead is 24 bytes (20 bytes IPv4 header + 4 bytes GRE Header), thus the default setting for an IPv4 MTU is 1,476.
   MTU6	Set an IPv6 tunnel‘s MTU from 128 - 1,456. The MTU is the largest physical packet size (in bytes) transmit able within the tunnel. Any messages larger than the MTU are divided into smaller packets before being sent. A larger MTU provides greater efficiency because each packet carries more user data while protocol overheads, such as headers or underlying per-packet delays, remain fixed; the resulting higher efficiency means a slight improvement in bulk protocol throughput. A larger MTU results in the processing of fewer packets for the same amount of data. For IPv6, the overhead is 44 bytes (40 bytes IPv6 header + 4 bytes GRE header), thus the default setting for an IPv6 MTU is 1,456.

3. In the Peer table, review credentials of existing GRE tunnel end points. If needed, click + Add Row to add new GRE tunnel peers. A maximum of two peer configurations can be added.

   Peer Index	Assign a numeric index to each peer to help differentiate tunnel end points.
   Peer IP Address	Define the IP address of the added GRE peer to serve as a network address identifier.

4. Define the following Failover parameters:

   Enable Failover	Select this option to periodically ping the primary gateway to assess its availability for failover support.
   Ping Interval	Set the duration between two successive pings to the gateway. Define this value in seconds from 0 - 86,400.
   Number of Retries	Set the number of retry ping opportunities before the session is terminated.

5. Select the OK button located to save the changes.

   Click Reset to revert to the last saved configuration.