ISP Dodo played a role in causing the outage that affected millions of fixed-line and mobile internet connections across the country this afternoon, Dodo's chief has confirmed.

"To be perfectly frank the extent of what happened was more than anybody could've thought," Dodo managing director Larry Kestelman told this website in an interview, adding his team was still investigating exactly what caused the issue.

Dodo MD Larry Kestleman.

"What it looks like has happened ... is a very minor hardware failure on one of the routers that has caused some big issues between ourselves and Telstra and had a flow on effect to others which it absolutely shouldn't have," he said.

"Telstra is saying that there were some overseas routing issues as well - but to me it sounds like it was a combination of things that caused it."