By default, authorized users can access your enterprise from any IP address. You can restrict access to specific IP addresses such as your physical office locations by contacting support.
Contact GitHub Support with the IP addresses that should be allowed to access your enterprise. Specify address ranges using the standard CIDR (Classless Inter-Domain Routing) format. GitHub Support will configure the appropriate firewall rules for your enterprise to restrict network access over HTTP, SSH, HTTPS, and SMTP. For more information, see "Receiving help from GitHub Support."