You can retrieve a list of GitHub's IP addresses from the meta API endpoint. For more information, see "Meta."
These ranges are in CIDR notation. You can use an online conversion tool such as this CIDR / VLSM Supernet Calculator to convert from CIDR notation to IP address ranges.
We make changes to our IP addresses from time to time, and will keep this API up to date. We do not recommend allowing by IP address, however if you use these IP ranges we strongly encourage regular monitoring of our API.
For applications to function, you must allow TCP ports 22, 80, 443, and 9418 via our IP ranges for github.com.