When @jmpesp was testing #3387 in the Canada region, we tried running with a RackNetworkConfig of:

[rack_network_config]
gateway_ip = ""
infra_ip_first = ""
infra_ip_last = ""
uplink_port = ""
uplink_port_speed = "speed_10g"
uplink_port_fec = "none"
uplink_ip = ""

This is "valid" as far as type type system is concerned: the two enum values (uplink_port_{speed,fec}) have valid values, and the remaining values are all Strings; however, attempting to run RSS with these values eventually failed with

Bad configuration for setting up rack: unable to parse rack_network_config.uplink_up as IpAddr: invalid IP address syntax

If we're trying to parse values as IpAddr, I think we should be able to make the fields IpAddr from the top.