External network route advertisement validation

A computer-readable storage medium, which is non-transitory, including instructions that upon execution cause a computer system to:

• at a source network, generate a probe packet including a destination network address field, the destination network address field including a network address in a range associated with a network prefix that was previously announced to an external network;
• transmit the probe packet from the source network to the external network, wherein the destination network address field includes the network address for a destination within the source network;
• and
• monitor packets received at the source network from the external network to detect whether the probe packet has returned to the source network.

A network device, comprising:

• a controller configured transmit an update packet from a source network including the network device to a neighboring external network, the update packet announcing a network prefix associated with a range of network addresses in the source network;
• switching logic coupled to the controller, the switching logic including hardware configured to:
• transmit a probe packet from the source network to the external network, the probe packet including a destination network address field identifying a destination network address having the announced network prefix, wherein the destination network address is within the source network from which the probe packet is being transmitted;
• and
• monitor incoming packets received from the external network to detect whether the probe packet has returned to the network device;
• wherein the controller is further configured to initiate validation of the announcement of the network prefix to the external network responsive to detecting that the probe packet has returned to the network device.