In the BFD echo support scenario, the 7210 SAS loops back received BFD echo messages to the original sender based on the destination IP address in the packet.
The echo function is useful when the local router does not have sufficient CPU power to handle a periodic polling rate at a high frequency. As a result, it relies on the echo sender to send a high rate of BFD echo messages through the receiver node, which is only processed by the receiver forwarding path. This allows the echo sender to send BFD echo packets at any rate.
The 7210 SAS supports only response to echo requests and does not support sending of echo requests.