To ensure our service can be used to its maximum potential and experience the best performance it's important that the hardware on which a GRE tunnel is terminated supports GRE offloading. This is a feature provided by the manufacturer of your NIC. On unsupported hardware there can be severe performance hits primarily to the amount of bandwidth which can go through the GRE tunnel. Without offload all GRE encapsulation must be done by the CPU which will slow down and limit your traffic.
Linux
On linux the simplest way to check what offloads are supported is with ethtool.
ethtool -k eth0 | egrep 'gre'In the output you should see a line such as tx-gre-segmentation: . Possible values are as follows.
-
on- offload is supported, and enabled. -
off [fixed]- offload is not supported, and not enabled -
off- offload is supported, but not enabled.
Mikrotik
To enable GRE hardware offload on Mikrotik you must enable fast-path on the interface. Please read about fast-path here. Not all models and software versions support fast-path please consult with the vendors documentation to ensure your setup does.
To configure fast-path on your tunnel check the documentation for the properties to configure.
https://help.mikrotik.com/docs/spaces/ROS/pages/24805531/GRE#GRE-Properties
Other Vendors
Most other major vendors ( Cisco, Juniper, Arista, etc) support GRE offload. Please consult with the vendors support or documentation to ensure your specific model is supported in its current configuration.
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