Pros
Lots of resources to work on projects, comfortable working environment, and you get to work on products that are used at scale by a lot of people.
Cons
Management is a disaster, incompetence is rife, and you always know that your product is being run into the ground with executive management thinking about when, not if, they are going to cancel it. Cisco is a machine for extracting value from acquisitions: it buys companies and then strip-mines them. Good people leave to find better jobs and the people who can't find better jobs are promoted based on tenure rather than ability. Every Cisco office starts out decent and gets progressively worse. There's a running joke that if you're ever handed a brief for a new product then you should quit and start your own company to build it, because Cisco will buy your company for a lot more than they would have paid you and you'll get to take all the good people (and only the good people) with you. Don't look for career advancement here; if you don't enter the company as executive management then you are an expense to be reduced.