Juniper Networks, which makes high-end devices that route traffic around the internet, looked to be making headway in a key growth market a few years ago when it started selling its routers to Amazon Web Services. AWS is the biggest of the public cloud providers that handle an increasing share of big companies’ computing work.

But hopes that AWS could jumpstart Juniper’s stagnant growth may have been premature. Over the past few quarters, AWS has been replacing some of its Juniper routers and switches with its own custom-designed hardware, said two people with direct knowledge of the change. The move, which hasn’t previously been reported, appears to be part of a broader move by AWS to gradually replace networking hardware made by other companies with homegrown alternatives, said one of the people.