GRE Tunnel

ExtremeXOS 15.4 and later supports creating a Generic Routing Encapsulation (GRE)-based IPv4 tunnel, and routing IPv4 traffic over it. This feature is supported on all platforms that have GRE tunneling support (see ExtremeXOS 32.4 Feature License Requirements ).

ExtremeXOS 31.3 and later supports GRE tunnel configuration on user VRs instead of only on the Default VR. You can also configure the L3/IP interface of GRE tunnels on different VRs than the VR for the endpoints (source and destination IP addresses) using the revised create tunnel tunnel_name gre destination destination-address source source-address {vr vr_name} {payload-vr payload_vr_name} command.

Note

Only one BGP session is recommended over a GRE tunnel that is configured in user VRs.

Note

The tunnel can be configured on user or default VR, but cannot be configured on VR-control and VR-mgmt.

As switch administrator, you can configure a GRE tunnel by supplying the local source IPv4 address and the destination IPv4 address. When configured, traffic can be redirected through the GRE tunnel. The TTL value of the outer IPv4 header is set to 255, and the DSCP value is copied from the inner IPv4 header, the same as for the IPv6 tunnels. The encapsulated packets do not include the GRE checksum option; however if received with a checksum they are verified by the software, and then dropped if incorrect. The GRE module is capable of dealing with RFC 1701 neighbor options, with the exception of the router option. Packets with this option set are dropped. However, hardware does not support any options in the GRE header. If any of these options are set, the packet is either dropped, or sent to the CPU for processing. Since the key option of GRE tunnel is not configured, the GRE module only accepts GRE packets with a key value of 0, if present, and drops packets with other key values.

Note

GRE tunnels are IP tunnels, which require L3 function. L3 features are supported with an Edge or Base license or greater. All of the supported platforms' default license is Edge\Base or greater, which include L3 features.

All nodes in a stack need to support GRE tunnels, or else the feature cannot be configured/enabled. When all nodes in the system are capable of running GRE, new GRE tunnels can be created. If a new node is added to a stack that does not support GRE, when it is powered on, a log message is generated indicating that the node is not compatible with GRE, and should be removed. If a stack boots up with both a GRE configuration and a GRE-incapable node, all GRE tunnels are put in a system disabled state. This is done to prevent the node from continuously rebooting. The show [{tunnel} {tunnel_name} | tunnel {vr [vrname | all]} {payload-vr payload_vrname} {detail] command displays this.