As mentioned earlier, Flannel supports multiple different backend configurations. A backend is considered to be the means by which Flannel passes traffic between Flannel-enabled hosts. By default, this is done through UDP as we saw in the previous recipe. However, Flannel also supports VXLAN. The advantage to using VXLAN over UDP is that newer hosts support VXLAN in the kernel. In this recipe, we'll demonstrate how to change the Flannel backend type to VXLAN.
It is assumed that you're building off the lab described in the previous recipes in this chapter. You'll need Flannel-enabled hosts that are integrated with Docker as described in the first two recipes of this chapter. In some cases, the changes we make may require you to have root-level access to the system.