The tx-ring-limit is automatically tuned only when the fair-queue command is configured on a interface. Therefore, if the no fair-queue command is configured on an interface, the serial interface hardware transmit buffer does not necessarily have the correct setting for the tx-ring-limit.

Also, when an individual link is part of a dialer group or multilink group, the link configured for the master interface is the one actually queued. If the fair-queue command is configured for the interface serial0/0, it automatically tunes its ring-size for low latency operation. At the same time, traffic is shaped as configured for the master multilink interface.