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M2M Cellular Gateway
5.5.9 GRE
Generic Routing Encapsulation (GRE) is a tunneling protocol developed by Cisco Systems that
encapsulate a wide variety of network layer protocols inside virtual point‐to‐point links over an
Internet Protocol internetwork.
Deploy a security gateway for local office and establish a virtual private network with the remote
gateway of another office by using GRE tunneling. So, all client hosts behind local security gateway can
make data communication with others behind remote gateway. The most popular scenario is the
security gateway is located at a branch office. Employees in the branch office want to use their client
hosts or devices behind the security gateway to access the resources in headquarters. These resources
are located in the Intranet of headquarters, and the security gateway in headquarters supports the
GRE tunneling function. Then local security gateway can establish a GRE VPN tunnel with remote
gateway in headquarters. Client hosts in these both Intranets of branch office and headquarters can
make data communication each other.
In "GRE" page, there is a "Configuration" window to enable the GRE VPN function. In addition, the
"GRE Tunnel List" window lists all your defined GRE tunnels. GRE is a peer to peer tunneling between
two gateways. So, one set of parameters can be used for these both gateways to establish a GRE VPN
tunnel by matching all parameters each other. Add one new GRE tunnel by using the "Add" button, and
edit one existed tunnel by using the "Edit" button. At last, the "GRE Rule Configuration" window lets
you specify all required parameters for a GRE tunnel.
A security gateway can be the client and server for a GRE tunnel at the same time. That is, the
security gateway, configured as a client, can initiate the establishing of one GRE tunnel while taking a
request for tunnel establishment from a remote GRE client security gateway, even using the same set
of configuration settings.
Configuration
Index skipping is used to reserve slots for new function insertion, when required.
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