Customers of budget internet service providers Dodo and ClubTelco across Australia were left without a stable internet connection for at least 12 hours on Monday after technical issues caused intermittent or slow connectivity.
In a statement at about 8pm on Monday, Dodo said the problem was due to "a hardware failure" in its Victorian network.
"Our network operations team identified the issue and has treated it with the highest priority, expecting to restore the network to full operations this evening. We apologise to all customers affected by the outage," a company spokeswoman said.
Broadband outage website Aussie Outages showed several hundred customers complaining from about 7am AEST Monday.
As of 3pm, the site - which takes submissions from the public - showed the issues appeared to remain for some. At 4pm they peaked again.
Broadband forum Whirlpool also had a number of users complaining.
As of 2011, Dodo had around 300,000 customers while ClubTelco, which is owned by the same company, had 120,000. M2 Telecom acquired both companies last year and its website was offline Monday afternoon too.
Subscribers of other M2 companies, Eftel and aaNet, also reported problems on Whirlpool.
"This is our highest priority and our technical support team are currently working hard to resolve this service outage."
The junior ISPs said their telephone contact centres were affected by the outage and the best way to get in touch was via live chat on their websites. But at times on Monday both websites were unreachable.
"We appreciate your patience while we try to manage the heavy traffic on Live Chat at this time. Otherwise we will make sure to answer your queries on Facebook as well," Dodo said in its post.
"Regular updates will be shared via our Facebook and Twitter profiles as we work towards resolving this issue.
"Please accept our sincerest apologies for this inconvenience. We thank you for your understanding."
Dodo and ClubTelco weren't the only ones suffering outages this week. Tech publication Lifehacker reported that some Telstra 4G hotspot users were also having issues connecting to the web thanks to a faulty software update.
In 2009, reports surfaced that Dodo's network performance and customer service woes had plumbed to new lows, with the internet provider's customers reporting cripplingly slow browsing speeds for a period of two weeks.
In 2012, the company took blame for an outage affecting many Australian internet connections, saying it was caused by a hardware fault on a router that triggered crippling flow on effects at Telstra.