Flannel use interface for inter-host communication setted on --iface options
Defaults to the interface for the default route on the machine.
flannel config set via daemonset, and flannel config on all nodes is the same.
But different nodes can have different interface names for the inter-host communication network
The option --iface-regex allows the flannel to find the interface on which the address is set from the inter-host communication network
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