Native GRE Tunnels

Generic Routing Encapsulation (GRE) is a lightweight tunneling protocol that encapsulates L3 traffic in an L3 and GRE header. The 128T Networking Platform now supports both a GRE plugin as well as native GRE tunnels.

note

This is not an SVR feature. GRE tunnels are not created to send packets between peered 128T routers. However, a packet coming from SVR can egress into a GRE tunnel, and vice versa.

Sending Packets

When a GRE tunnel is configured, sessions are set up to and from the endpoints. With a GRE tunnel configured as a possible path for the service, the load balancer has the option of choosing the tunnel as the packet’s next hop.

When the tunnel is selcted as the next hop the session sets up normally, and the the appropriate headers are added for the tunnel.

Receiving Packets

On the receiving end, a static flow is created to receive all traffic coming from that tunnel. When a GRE encapsulated packet arrives, the tunnel headers are removed and the packet is forwarded to the normal lookup path. If a session exists, the packet is processed by the corresponding flow. If the session for this packet does not yet exist, a session is created.

Configuration

Use the following information to configure a GRE tunnel.

Interface Configuration

Network-interfaces can be configured as gre-tunnels. These interfaces are virtual interfaces, which must share a VLAN tag with a non-virtual interface. The shared VLAN tag indicates which non-virtual interface the tunnel is associated with.

Configuration from the GUI

The following procedure describes configuring a GRE Tunnel using the GUI.

  1. Under Configuration, select the Router.
  2. Scroll down and select the Node.
  3. Select the Device Interface.
  4. Scroll down to Network Interfaces and click ADD.
  5. Enter a name for the device interface and click SAVE.
  6. Under Type, select GRE Tunnel.
  7. Under Network Interface Tunnel Settings, choose either Inherited or Custom. The Source is the IP address of the start the tunnel. It can be inherited from the associated non-virtual network interface, or configured explicitly using Custom.
  8. Add the Destination IP address for the tunnel.
  9. Click Validate and Commit.

PCLI Configuration

The following example configuration describes using the PCLI to configure a GRE Tunnel. Router and node configuration are provided for context:

router Router128
name Router128
location usa
node test1
name test1
enabled true
  1. Create a device interface GRE.
device-interface GRE
name GRE
type ethernet
pci-address 0000:00:06.0
  1. Create a non-tunnel interface, base.
network-interface base
name base
global-id 2
tenant red
address 172.16.3.1
ip-address 172.16.3.1
prefix-length 24
exit
exit
  1. Create a tunnel interface, tunnel. This is the virtual interface representing the tunnel. Set the type field to gre-tunnel.
network-interface tunnel
name tunnel
global-id 3
type gre-tunnel
tenant red

Please note that in this configuration, the base interface and the gre-tunnel interface tunnel share the same vlan. For this to work, they must be on a single device-interface.

  1. Create the tunnel container with a destination of the IP address for the destination of the tunnel. The source identifies how the local IP address is obtained. Setting it to network-interface acquires the address from network-interface-base.
tunnel
destination 172.16.3.2
source
network-interface
exit
exit
exit
exit
exit
  1. Create two service-routes for the tunnel, an outbound and inbound. Be sure to specify the virtual tunnel interface as the outbound service-route interface.
service-route gre-outbound
name gre-outbound
service-name gre-outbound
next-hop test1 tunnel
node-name test1
interface tunnel
gateway-ip 172.16.3.2
exit
exit
service-route gre-inbound
name gre-inbound
service-name gre-inbound
next-hop test1 eth
node-name test1
interface base
exit
exit
exit

Tunnel Statistics

The following tunnel encapsulation statistics provide details on encapsulation and decapsulation success, as well as failure modes.

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