What evidence do auditors commonly ask for on COS-07 Documentation of the network topology?

Current logical network drawing carrying a revision date and a named owner; Subnet allocation register mapping address ranges to zones and purposes; Evidence that the drawing is amended as part of every network change; Statement of the physical sites at which customer data is held.

What is the most common gap auditors find on COS-07?

Drawings predate recent network work, so live routing differs from what is depicted

BSI C5 (121-criteria catalogue) · C5: Communication Security

`COS-07` Documentation of the network topology

Keep traceable and current documentation of the logical network used to provide the service, showing subnet allocation, zoning and segmentation together with the geographic locations holding customer data, to avoid administration errors and enable timely recovery.

Source: BSI C5 (121-criteria catalogue), COS-07. The statement above is our statement of the clause, read from the published text and cited so you can check it against the official text, not the instrument verbatim. Open BSI C5 (121-criteria catalogue) in the compliance library.

The edition of the catalogue is not stamped here; check the edition your attestation is issued against.

artefacts

held by a system

at each review

hard

to go live

Policy repository / GRC workspace

where the evidence lives

teal = a system already holds it · olive = produced at each review. To go live: easy when half or more of the artefacts are already held by a system, moderate from a quarter to a half, hard below a quarter.

These are the artefacts auditors commonly ask for on this requirement, our guidance rather than text from the standard. Your assessor decides what is sufficient in your context, and asks for samples across the period when a report covers one.

system holds itEvidence a system already holds

none for this control

periodic reviewEvidence produced at each review

Evidence that the drawing is amended as part of every network change · Cloud console / configuration management

governing documentDocuments that govern the control

Current logical network drawing carrying a revision date and a named owner · Policy repository / GRC workspace
Subnet allocation register mapping address ranges to zones and purposes · Policy repository / GRC workspace
Statement of the physical sites at which customer data is held · Policy repository / GRC workspace

First move

No system holds this evidence for you: it is people and documents. Reminders and routing to the owner still save time. Put the document under version control with an owner and review date, and log each review as a record with reviewer and date.

Common gaps auditors find

Drawings predate recent network work, so live routing differs from what is depicted
Storage locations omitted, leaving customers unable to assess data residency
No accountable owner, so updates depend on whichever engineer remembers

Do this for your whole sheet

Paste the rows you run your controls from and get this mapping for every control at once, with the periodic-review ones flagged and a first move per row. No account for the first run.

Build my evidence sheet

COS-06 Segregation of data traffic in jointly used network environments · COS-08 Policies for data transmission