Optus says “changes to routing information” following a “routine software upgrade” were to blame for last week’s nationwide outage, which affected 10.2 million Australians and 400,000 businesses.
In a statement released on Monday afternoon, Optus said its network was affected by “changes to the routing information of an international peering network” at around 4:05am AEDT last Wednesday, “following a routine software upgrade”.
“These changes to routing information propagated through multiple layers in our network and exceeded preset security levels on key routers that could not handle them,” the company said.
“This resulted in the routers disconnecting from the Optus IP Core network to protect themselves.”
The extent of the outage meant Optus engineers had to physically reconnect or restart the system, the telco said, and also meant the investigation into the cause “took longer than we would have liked”.
“The restoration required a large-scale effort from the team and in some cases required Optus to physically reconnect or reboot routers, requiring people to be sent to a number of locations in Australia,” an Optus spokesperson said.
“This is why the recovery was gradual throughout the afternoon.
“Given the widespread impact of the outage, the investigation into the issue took longer than we would have liked as we explored various paths to recovery.
“Restoring the network was our priority at all times and we then set up the business together with our partners.”
Optus says it has since made changes to its network to address the issue so it doesn’t happen again.
It comes after Optus made an extra 200GB of data available to customers from Monday to compensate for last Wednesday’s outage.