The 37-year-old had been training with League Two outfit Cambridge United but turned down a contract offer from them in favour of a move to the A-League, The Irish Sun reports.
He spent last season with West Bromwich Albion after a decade at Norwich City, making over 300 appearances. He is believed to have been considering a move Down Under after leaving Norwich.
Cambridge coach Colin Calderwood was hopeful of keeping the midfielder but accepted he was moving to the A-League.
“There’s a nice opportunity for him, we’ve got no hold on him," he said.
“We wish him all the best, it’s a blow for us. Every indication was that he was going to be a very important factor in helping us achieve what we want to achieve this season.
“I really enjoyed having him around the environment and he’s definitely helped everyone.”
