IP allow list

How it works

It helps for stable server IPs. It fails for home users and cloud egress that changes. A new NAT address looks like an attack. Pair it with a key, not instead of one.

A partner SFTP host allows two egress IPs. A cloud job moves to a new NAT and cannot connect. The key is valid. Updating the list restores the 01:15 feed. A traveler on a laptop was never going to fit this control.

How it differs

An allow list is not authentication. A stolen key from an allowed address still works.

Cloud providers publish wide ranges. Allowing the whole range is barely a control.

Pin the egress you own.

On the ticket

• The practical close is a log line: time, actor, byte count, result.
• Without that line the transfer is a story.
• With it, the next person can see whether this door did what the ticket claimed.
• If the path is shared, say so in the partner profile so a later change does not silently pick a different limit, key, or region.
• On a real ticket, write down the door, the byte count, and the clock.
• For ip allowlist, that means naming the host or bucket, the expected size, and the time the other side must have a complete file.
• A progress bar is not that record.
• A 200 response that arrives before the complete call is not that record.
• If a retry is allowed, say how many and whether it resumes.
• If a person must approve the send, name the person.
• Partners who receive ip allowlist files should match on hash or size before they import.
• A same-length corrupt file passes a size check and fails a hash.
• Keep the published hash off the only channel an attacker can edit, or treat it as a corruption check rather than a substitution check.
• When the path changes, new key, new region, new cap, update the profile the same day so the next run does not use a stale limit.