We have to call the Companies House API from a server where external access to Internet is blocked. We can whitelist an IP address or range of IPs to be allowed from the server. Unfortunately we can't whitelist an URL. Can you please provide us with the range of IP addresses that we need to open from our firewall? We have seen that the IP addresses are dynamically assigned and for Companies House API URL and nslookup IP addresses are also seem to be dynamic because the API is hosted on cloud.