Thank you @kevink and @Alexey for your answers but I don’t think I was clear enough with my question.
When my storagenode is behind carrier grade NAT, my internet traffic comes from a public IP that I can find from visiting https://www.yougetsignal.com/tools/open-ports/. If I am using portmap.io, I will provide the storage node with the portmap.io hostname, but that will resolve to a different IP address than my other outgoing internet traffic.
So my initial announcement to the storj network will come from my external IP address which then provides the network with my portmap.io hostname to use for incoming traffic.
So my question is, when the network is choosing a random /24 to select a node, does the network use the portmap.io hostname/IP address I provided, or my external IP address where my outgoing traffic appears to be coming from.
(I’d like to note that since portmap.io is not a VPN, no new outgoing connections will be made through it, only replies to connections came in through portmap.io.)