Hello. Thank you for your interesting question!
Because IP addresses, subnet masks, and binary numbers are technical terms, I would use Nemeth for all three renditions of this notation -- both in narrative context and within a mathematical expression. I would use the (46) symbol in all cases. Here is my reasoning.
I find this IP address notation (and subnets) being referred to as "dotted decimal notation" and "binary point" in binary notation, so the use of a (46) symbol for this dot is not out of line. It certainly will be smoother reading to use (46) rather than (456, 256, 3456) for every "period".
State your usage in a TN, using the terminology for the dot that is used in the print document. I would not refer to (46) as a "decimal" since that word implies base 10. For example, if the text calls it a "period", here is a possible TN: "The symbol (46, 123456, 46) represents the period used to separate groups of numbers in the IP addresses, subnet masks, and binary representations."
I look forward to your followup response.