AS8070 MICROSOFT-CORP-MSN-AS-BLOCK

A large Microsoft Autonomous System in the MICROSOFT-CORP-MSN-AS-BLOCK range,

announcing roughly a million IPv4 addresses of Azure and Microsoft service space.

What it's used for

• Azure workloads and Microsoft's own online services. Its inventory spans both the classic Microsoft blocks (131.253.120.0/22) and the very large modern Azure allocations (20.34.0.0/15, 52.126.0.0/15, 57.16.0.0/14).
• Some of it is Azure Government: addresses in 204.13.120.0/21 resolve to azuregov-dns.us nameservers.

Notable

• An IP here identifies Microsoft as the host, not the operator of whatever is running on it — the same address block can front a first-party Microsoft endpoint or a customer's Azure deployment.
• Reverse DNS is largely absent, which is normal for Azure. Microsoft publishes its service IP ranges as machine-readable lists precisely because you cannot infer them from DNS.

Interesting

• The presence of Azure Government space means part of this AS is subject to a separate, isolated US-government cloud environment, even though the AS itself looks like ordinary commercial Microsoft space from the outside. See [AS8069](https://asn.ipinfo.app/AS8069) and [AS8075](https://asn.ipinfo.app/AS8075) for sibling Microsoft ASNs.