Cisco CCNP / BCMSN Exam Tutorial: Multicasting And The RPF Check
Posted in Computers on June 7th, 2009 by cahyoMulticasting is a vital topic on your BCMSN, CCNP, and CCIE exams, and it can also be very confusing when you first start studying it. Multicasting uses concepts that are unlike anything you’ve run into in your routing protocol studies, and that can throw you at first. I speak from experience that multicasting is like any other Cisco technology – learn the basics, master the fundamentals, and then build your skills on that foundation.
One such fundamental is the RPF Check, or Reverse Path Forwarding Check.
A fundamental difference between unicasting and multicasting is that a unicast is routed by sending it toward the destination, while a multicast is routed by sending it away from its source.
“toward the destination” and “away from its source” sound like the same thing, but they’re not. A unicast is going to follow a single path from source to destination. The only factor the routers care about is the destination IP address – the source IP address isn’t a factor. Read more »