Cisco Networking Engineer interview questions

I first had a 20 minute phone call. They asked basic network questions and maybe a few behaviour question. e.g. of behavioural question being when was a time when you had to work as a team? Networking question example is what is DDoS? The assessment centre interview went pretty well until the technical question came along. They asked what you can do to find out why the new router that was implemented is not working correctly. I was unprepared, involved subnetting. First part of interview was team-work, then it was technical question, and finally panel interview asking behavioural questions.