Juniper Networks increased its share of the edge router market in the second quarter at the expense of its larger rival, Cisco Systems, but Cisco made greater gains in the core router market, according to data released this week from Dell’Oro Group.

Sales of Juniper’s edge routers grew 17% sequentially in the second quarter while Cisco’s slid 3%, according to Dell’Oro. As a result, Juniper raised its share of the edge router market from 2% to about 29%, while Cisco’s share shrank from 65% to 61%.

However, Cisco grew faster than Juniper in the market for core routers. Sales of Cisco core routers grew 12% sequentially in the second quarter (a 42% year-over-year increase), while Juniper’s grew 5% sequentially (up 53% year-over-year). Juniper steadily increased its share of the core router market at Cisco’s expense last year, while Cisco introduced a new product, the massive CRS-1, in May 2004.

Both vendors lost share in the core router market in the second quarter, however. Cisco’s share dropped from 65% to 64%, and Juniper’s dropped from 27% to 25%. Alcatel grew its share of the core market from 0.8% to 2.8% in the quarter, due mainly to shipments of its 7750 edge router (which can be used in the core) to France Telecom.

The overall global router market grew more in the second quarter of 2005 than it has since 2000, growing 8% sequentially to reach $2.5 billion, Dell’Oro said.

Cisco also benefited from its No. 1 position in the Ethernet switch market, which grew 8% in the second quarter to nearly $3.5 billion after two quarters of decline.