Why does the BSI registration ask for our public IP address ranges?

Because section 33(1) of the BSIG lists them among the contact data entities must submit, so that the BSI can match warnings to the right organisation. When the BSI or a partner learns that an address in your range is part of a botnet, runs a vulnerable service or is under attack, it needs to know whose address it is to warn you quickly. In practice, many companies do not know their ranges offhand: they may be assigned by an internet provider, split across sites or spread over cloud services. Collect them from your provider contracts and router configuration, record which belong to which site, and keep the list current, since changes must be reported within two weeks under section 33(5). The registration does not authorise anyone to scan or attack those addresses. NetSenX does not register you, but its network view shows which internal devices talk to the outside through which addresses.

General information, not legal advice. National laws can add to the EU texts quoted here, for example deadlines, forms or reporting channels: check your own country's rules.

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