In the two years since he replaced John Chambers as Cisco Systems Inc.'s (CSCO) CEO, Chuck Robbins has spent billions on software and cloud services acquisitions, overseen a few big internal software and services product launches and revamped Cisco's leadership teams for multi-billion dollar product lines.

None of that, however, prevented Cisco from reporting a 3% annual July quarter revenue drop and guiding for a 1% to 3% October quarter drop amid a slew of pressures for its mainstay switching and routing franchises. Robbins likely wants Cisco to see bigger changes still, both in terms of its product line and culture, and he should soon have the freedom to carry them out.

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On Monday, Sept. 18, Cisco disclosed that Chambers, who had remained executive chairman following his resignation as CEO, won't seek re-election to Cisco's board at the company's Dec. 11th annual meeting. Robbins will take over as chairman, and Cisco's board size will be cut to 11 members from 12.

Markets brushed off the news: After opening slightly lower, Cisco closed up 0.3% to $32.52. Shares are up 7.6% on the year, compared with an 11.7% gain for the S&P 500 and a 19.9% gain for the Nasdaq.

Cisco's announcement came just five days after The Information reported of ongoing tensions between Chambers and Robbins, as Robbins gradually put his mark on the company. Among other things, it mentioned the pushback Robbins received from Chambers and four Cisco execs over the appointment (just after Robbins became CEO) of Biri Singh, formerly the head of HP and IBM's cloud services businesses and before that the CEO of multiple software startups, as Cisco's CTO.

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Singh would leave Cisco in October 2016 following a management shakeup that put Cisco's "engineering and development efforts" under the oversight of networking/security product chief David Goeckler and IoT/applications chief Rowan Trollope. But not before the four execs backing Chambers left, following Robbins' decision to cut back on a Chambers-era practice of funding and later acquiring startups (known as spin-ins) created by top Cisco engineers to build new products. Regardless, it's telling that Singh's hiring was an apparent flashpoint for tensions between Robbins and Chambers, given Singh's software-centric background and (judging by the interviews he gave while at Cisco) vision for Cisco's product line.

Since Robbins was named Cisco's next CEO in May 2015, his company has made at least 13 software and services-related acquisitions, with the total value of deals for which a dollar figure was given topping $8 billion. Cisco's $3.7 billion early-2017 purchase of leading app performance monitoring (APM) software firm AppDynamics is easily the biggest of the bunch; other notable purchases include IoT connectivity services provider Jasper Technologies ($1.4 billion-plus), collaboration/conferencing software firm Acano ($700 million), SD-WAN software firm Viptela ($610 million) and DNS service and security software provider OpenDNS ($635 million).

The Robbins era has also seen Cisco launch Tetration, a software platform that relies on sensors placed on Cisco and third-party devices to analyze how data center resources are used, and more recently DNA, a set of subscription software products that work with new Cisco campus switches to create big-picture policies related to how networking resources are managed, provisioned and secured. It has also seen a slew of security, IoT and collaboration software launches, and the rollout of suites and enterprise agreements meant to make it cheaper for businesses to deploy several software products at once.

All the same, Cisco's product revenue fell 4% annually last quarter (perhaps 2% after factoring the push-out of revenue recognition caused by subscription growth), thanks largely to 9% drops for both switching and routing revenue (software included). Switching and routing growth rates should improve as some near-term issues, such as the aforementioned campus switch transition and weak emerging markets telecom capex, go away or diminish. But plenty of other issues are likely to be around for a while.

These include the continued shift in both IT spending and enterprise workloads towards cloud infrastructures that use quite a lot of "white-box" switching gear based on open-source designs, as well as stiff switching competition from Arista Networks Inc. (ANET) , Huawei, Juniper Networks Inc. (JNPR) and HP Enterprise Inc. (HPE) . Cisco is also dealing with rising adoption of VMware Inc.'s NSX software-defined networking (SDN) platform, which (though working with Cisco switches) makes it easier to deploy commodity switches within data centers. As well as with a tepid telecom capital spending environment, as carriers seeing little or no revenue growth keep a lid on equipment purchases.

Against this backdrop, it wouldn't be surprising if Robbins, no longer having to worry about Chambers vetoing a deal, pushes for a much bigger software purchase than the ones Cisco has made to date. Open-source software giant Red Hat Inc. (RHT) , which sports a $19 billion market cap, is one intriguing target -- Red Hat isn't just the top player in a still-growing enterprise Linux market, but also now a major provider of middleware, storage software and cloud/data center management software, much of which goes into telecom and enterprise cloud deployments.

Cloud collaboration app vendor Atlassian Corp. (TEAM) ($8.3 billion market cap) and PC/app virtualization software leader Citrix Systems Inc. (CTXS) ($11.6 billion) are two other possibilities. And if Robbins chooses to step up Cisco's security M&A efforts, possible targets include FireEye Inc. (FEYE) , data security software firm Proofpoint Inc. (PFPT) and security/compliance software firm Qualys Inc. (QLYS) .

In addition to new acquisitions, Robbins could push to have Cisco's biggest networking software platforms, such as DNA and the company's ACI data-center SDN platform, supported by cheaper hardware, rather than just costly switches running on Cisco's proprietary ASICs. A March report suggesting that Cisco wants to make software previously restricted to ASIC-based products available on switches powered by chips from the likes of Broadcom Ltd. (AVGO) fits with such an effort, and just might help Cisco better compete against Arista for the business of cloud giants.

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And as Light Reading's Craig Matsumoto points out, one could also see greater attempts to overhaul Cisco's corporate culture. "Engineering is certainly important to Cisco, but stories from the inside during the Chambers tenure described a sales-focused organization, one where products and divisions are pitted against one another in a model resembling economic markets," Matsumoto says. Microsoft's culture was often described in similar terms during the Steve Ballmer years; gradually, things have changed under Satya Nadella.

Overall, Chambers' track record at Cisco looks better than Ballmer's at Microsoft. But for both of them, the final years of their tenures at the tech giants they led were marked by the arrival of big secular trends that made it crucial for their companies to overhaul cash-cow businesses and make big investments in growth markets.

And for both companies, there's something to be said for having these moves carried out by new leadership that doesn't have to concern itself with the strategic decisions of predecessors.

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