Provider network in Installation Guide

Why in doc says:
"The --provider-physical-network provider and --provider-network-type flat options connect the flat virtual network to the flat (native/untagged) physical network on the eth1 interface"

Why eth1?
My controller has 2 network interfaces,one connected to the management network and one connected to the provider network. None of them are named eth1.

Should i just use the actual name of the controller interface that is connected to provider network?

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Release: on 2021-07-23 18:07:04
SHA: fbabdbc9ecf36d94d5e6097d613857bdc778bfd4
Source: https://opendev.org/openstack/openstack-manuals/src/doc/install-guide/source/launch-instance-networks-provider.rst
URL: https://docs.openstack.org/install-guide/launch-instance-networks-provider.html