December 6, 1999 Web posted at: 8:57 a.m. EST (1357 GMT) by Denise Pappalardo

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(IDG) -- The AT&T WorldNet dial-up network outage that took place most of the business day on Wednesday of last week was caused by another ISP, according to AT&T.

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Hundreds of thousands of its dial-up Internet access service users around the country could not access the Internet from 8:15 a.m. until about 4:30 p.m. December 1.

An ISP that AT&T WorldNet interconnects with changed its routing tables to mimic those on AT&T WorldNet's network, explains Rose Klimovich, director of global IP network services at AT&T.

This change caused problems on AT&T WorldNet's domain name servers which essentially put users in a black hole when they tried to access the Net.

"When our users tried to get to a Web site those requests were being sent to the wrong place," Klimovich says.

AT&T WorldNet supports approximately 1.8 million dial-up users. While an AT&T spokesman couldn't pinpoint how many customers were affected by the network outage, he did say that just about all consumer users and all dial-up virtual private network service users could not access Web sites that were not on AT&T's network.