Symptoms

Under some circumstances TMM may core when using deterministic NAT due to a divide by zero error.

Impact

Traffic disrupted while tmm restarts.

Conditions

CGNAT using deterministic NAT mode and persistence enabled. This error only occurs if a previous connection created an address persistence entry using the second address. This crash is dependent on both the configuration and the traffic. When the number of subscriber addresses that disaggregates to a TMM is not evenly divided by the number of translation addresses that disaggregates to the same TMM, connections from one or more subscribers may be assigned to blocks from two translation addresses. Depending on the exact address ratio, there may be only one port using the second address. Due to an off-by-one error, the number of ports available for the second address may be set to zero when it should be set to one. This causes the divide by zero fault.

Workaround

None.

Fix Information

None

Behavior Change