Exetel has signed a two-year deal with Optus Wholesale, under which Optus will exclusively deliver National Broadband Network aggregation services to the ISP.
In May, Exetel signed a three-year 4G wholesale mobile contract with Optus.
The two companies have had a commercial relationship since 2005.
Under the deal, Exetel will receive wholesale access to all of NBN's Points of Interconnect.
"We are excited by this NBN aggregation deal," Exetel CEO Richard Purdy said in a statement.
"It is an important stepping stone towards realising our aggressive NBN growth targets. We look forward to working with Optus as they help us keep our NBN pricing amongst the most competitive in the market."
Exetel last year marked its tenth anniversary. The company remains one of Australia's largest independent ISPs.