Verify Routing-Layer Permissions After a Stackup or Rule Change

A stackup change can leave routing permissions attached to outdated layer assumptions. The board may still route without obvious errors while a controlled signal uses a layer that engineering intended to exclude. Review layer permissions as part of the stackup-to-layout handoff.

Altium’s routing-rule documentation includes rules defining layers available for routing. Their practical use depends on rule scope and the routing workflow, so verify behavior in the actual design environment.

Translate the stackup decision into a layer policy

For each relevant net group, state the permitted signal layers and the reason for any restriction. Use physical layer identities and reference relationships rather than relying only on display colors or temporary names. Keep the policy aligned with the approved stackup revision. If a layer is renamed or reordered, verify the underlying physical assignment instead of assuming that a familiar label still refers to the same location in the stack.

Separate routing-layer permission from via-span availability. A net may be allowed on two layers while the available transition structure does not provide the intended connection between them. Both decisions need to agree.

Inspect scope and resolved behavior

Select representative nets from each restricted group and inspect which rule applies. Include one ordinary net outside the group to confirm the restriction has not unintentionally spread to the whole board.

Check old geometry separately

Do not assume a routing aid will automatically relocate or reject every pre-existing track after a policy change. Determine what the software checks, when it checks it, and whether imported or copied geometry receives the same treatment.

Inspect existing routes on newly excluded layers. Decide whether each occurrence requires rerouting, an approved exception, or a revision to the policy itself. Record the disposition so a future designer does not mistake a deliberate exception for the general rule.

Exercise a route attempt on both an allowed and an excluded layer in a validation copy. Observe the router’s behavior and any resulting report. This confirms that the configured tool supports the intended workflow, while the final geometry review establishes compliance of the actual board.

After resolving changes, regenerate relevant outputs and retain the layer-policy revision with the release. The resulting evidence should connect the electrical intent, approved stackup, routing constraints, and physical copper rather than relying on any single settings dialog as proof.