You can validate substitutions with the Enterprise portal.
When validating substitutions, the SRC software:
This feature allows SRC components, such as the policy engine, to interpret the expression 192.0.2.16/28 as an IP address and mask rather than a division operation.
The software will substitute the value of 123 for x, even though 123 is a rate and not an address. Eventually, however, the substitution will cause problems, and a component such as the policy engine or the SAE will reject the value.