Be prepared to give them descriptions of work that you've done that's related to the field. Issues you've ran into, how you troubleshooted them. Kinda like how you did in this post. They also love asking you the typical "describe at the packet level what happens when your computer wants to go to a website" etc. They expect you to go into how it works using ARP, DNS, TCP, etc.
I'm gonna assume you listed a bunch of technical terms in your resume? Go over them and be sure you know what they all mean. And just as importantly, go over your resume so you know exactly where everything is located in it. They'll likely want to go over it with you and you don't wanna look confused trying to find what's where in it. Bring a copy of your resume with you, in case they want it.
Prepare a couple questions you may want to ask them during or after the interview, in case you can't think of anything to ask during the interview process. It shows you're interested and serious.
Ask for the interviewer's business card or contact info after the interview, so you can send 'em a thank you email.
Quote from Osayidan;1069292:
Tell them cisco sucks donkey cock.
They'll either kick you out or give you the job on the spot.
D:<