# NAT gateway
<a name="nat-gateway"></a>

## Port allocation errors
<a name="port-allocation-errors"></a>
+ The alarm changes state if there is a port allocation error in the NAT gateway.
+ The alarm returns to the `OK` state if the data is within the acceptable threshold for 5 minutes.
+ This can mean that too many concurrent connections are open through the NAT gateway and it caused a port allocation error.
+ Metric: `ErrorPortAllocation` > 0

## Packets dropped count
<a name="packets-dropped-count"></a>
+ The alarm changes state if a value greater than 0.01% is reached within a 1-minute period.
+ This might indicate an ongoing transient issue with the NAT gateway.
+ The alarm returns to the `OK` state if the data is within the acceptable threshold for 5 minutes.
+ If this value exceeds 0.01 percent of the total traffic on the NAT gateway, check the AWS Service Health dashboard.
+ Metric: `PacketsDropCount` > 0.01%