When using istio’s egress gateway, if there is no separate setting, will the network timeout settings of envoy be used as is?

ex) idle timeout -> 1hour

Then, when outbound traffic is generated through egress, I am curious whether temporary port depletion of egress or maintenance of disconnected connections may occur due to the keepalive timeout or connection timeout settings of the destination server.

The reason I’m asking this question is, we migrated a server to a k8s environment.
After that, when we call API request from our server to the destination server, we intermittently received a 503 UC error. But the destination server said that it could not confirm the request.
Due to the overall structure, only egress, which is responsible for outbound traffic, was added, but it is doubtful that this is the start of the issue.