Pros
IMPORTANT - Different divisions within Cisco are vastly different from one another, my advice is to make sure you know if a GlassDoor review is relevant to the job that you are applying to. I work in the Collaboration Technology Group (CTG) which includes WebEx, TelePresence, IP Phones, Jabber and Spark (aka Project Squared). The Pro's of CTG are: (1) Typically your co-workers are great people. My immediate team, for example, is one of the top group of peers I've had in my whole career. They are smart, qualified and everyone cares about each other (2) The Collaboration Group has some really interesting products, there is a very good chance you'll work on something that is relevant and that you'll be proud to have on your resume (3) Cisco offers great benefits. I can almost guarantee you won't find a company that can beat what you get for being a full time employee (Medical, flexible work, 401k matching, etc)
Cons
The con's of working within the Collaboration Group: (1) At the VP and Director level Cisco is competitive and tumultuous, more so than any company where I've worked in 20+ years. In the last 5 years there have been 4 different Senior Vice Presidents and with each change there has been a lot of churn and changing of priorities. (2) There is a ton of in-fighting between groups (aka BUs or business units). Basically every Director and VP is incented to compete against ever other Director and VP for budget, resources, attention from executives & the sales force, etc). While this sounds normal for a large corporation, the stakes are high. Winners build set their own agedas and losers can not control their own products and often are subject to yearly layoffs. The bottom line is almost none of the teams are rowing in the same direction, rather everyone competes against each other. (3) Most importantly Cisco has a yearly layoff. Every July/August for the last 6 years the company lays off a large number of people. In that time the company has laid off more than 20,000 people and yet the number of employees is larger than ever. I've seen entire product teams get cut when other teams could sorely use the talented people that were let go. I know someone who got an Outstanding yearly review (which is only given to 6% of people at Cisco), and he was laid-off just a week later. Normally you think of a large company as being more stable than a small one, but Cisco is not at all stable (4) It's very hard at all levels to move up at Cisco. If you are a manager who wants to become a director it's very difficult, the best way to be a director at Cisco is to be at a company that Cisco buys. If you are a Tech Lead who wants to become a Senior Tech Lead the competition is fierce - I know several engineers that have been trying for years to make the next step.