Cisco is set to introduce a 3G module for its ISR line of branch and small-business routers. The 3G card will provide an Internet link via the EV-DO (Evolution-Data Optimised) or HSDPA (High-Speed Downlink Packet Access) networks of mobile operators that are working with Cisco, said Inbar Lasser-Raab, a director of marketing for network systems at Cisco.

However, the company has warned that VoIP calls to the outside world will not work - despite the VoIP capability of the ISR. The module doesn't officially support VOIP, which requires low delay, and mobile operators aren't guaranteeing call quality, Lasser-Raab said.

Most customers are likely to use 3G only as a back-up for when their main Internet connections go down, according to Lasser-Raab. But 3G has grown in both speed and coverage area over the past few years, to where Cisco says it is price-competitive with alternative back-up technololgies such as DSL and cable modem access and faster than ISDN. As faster wireless data technologies such as WiMax appear, Cisco plans to introduce new models.

Initially, customers can use the module on the Verizon Wireless, Sprint Nexteland AT&T Cingular networks in the US, as well as the Telefonica Moviles network in Europe.

3G could be more economical as a back-up than some alternatives, according to analyst Michael Brandenburg at Current Analysis. A large enterprise may get a discount on the connection if it has a big account with the carrier, he pointed out. However, if VoIP is required, they might treat it as a secondary backup, he said.

No other router company is offering such a module, according to Yankee Group analyst Zeus Kerravala. A wired backup such as ISDN is likely to go down along with the main connection anyway, he said.

"Being able to do it over another medium [airwaves] makes it a perfect backup technology for traditional leased-line access," Kerravala said.

The module is available in different models for HSDPA and EV-DO, with backward compatibility to slower technologies. It will be available in June through Cisco channel partners to customers who meet certain criteria, such as having adequate cellular coverage. US list price will be US$850.