Consolidation system &1 cannot be the same as the integration system

What causes this issue?

The integration system &1 was specified as the consolidation system.
The integration system and consolidation system must be different in a
transport route.
A system can only have both these roles in different transport routes
(transport layers).
Example:
Incorrect:
Integration system Transport layer Consolidation system
C11 ZC11 C11

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Correct:
Integration system Transport layer Consolidation system
C11 ZC11 K11
K11 ZK11 P11

System Response

The entry is rejected.

How to fix this error?

Enter a correct value.

Error message extract from SAP system. Copyright SAP SE.