Whenever you start your CCNA research, you get hit with plenty of completely different networking phrases instantly that you simply may not be conversant in. What makes it a bit of extra complicated is that plenty of these phrases sound so much alike. Right here, we’ll talk about the variations between broadcasts, multicasts, and unicasts at each the Information Hyperlink (Layer 2) and Community (Layer 3) layers of the OSI mannequin 플렉스티비.
A broadcast is just a unit of knowledge that each different gadget on the section will obtain. A broadcast is indicated by having each little bit of the tackle set to its highest attainable worth. Since a hexadecimal bit’s highest worth is “f”, a hexadecimal broadcast is ff-ff-ff-ff-ff-ff (or FF-FF-FF-FF-FF-FF, because the higher case doesn’t have an effect on hex worth). The CCNA examination will demand you be very conversant in hex conversions, so in case you’re not snug with these conversions, get snug with them earlier than taking the examination!
At layer 3, a broadcast is indicated by setting each bit within the 32-bit binary string to “1”, making the dotted decimal worth 255.255.255.255. Each host on a section will obtain such a broadcast. (Needless to say switches will ahead a broadcast, however routers don’t.) In distinction to a broadcast, a unicast is a packet or body with just one vacation spot.
There’s a center floor between broadcasts and unicasts, and that may be a multicast. The place a broadcast might be obtained by all, and a unicast is obtained by just one host, a multicast might be obtained by a number of hosts, all belonging to a “multicast group”. As you climb the Cisco certification pyramid, you may be launched to creating multicast teams and controlling multicast visitors, however to your CCNA research you want solely preserve sure multicast teams in thoughts.
Class D addresses are reserved for multicasting this vary is 224.0.0.0 – 239.255.255.255. The addresses 224.0.0.0 – 224.255.255.255 are reserved to be used by community protocols on a neighborhood community section, and like broadcasts, routers won’t ahead these multicast packets. (Packets with these addresses are despatched with a Time To Reside of 1.)
As a CCNA candidate, it is best to know that OSPF routers use the tackle 224.0.0.5 to ship hellos, EIGRP routers use 224.0.0.10 to ship updates, and RIP model 2 makes use of 224.0.0.9 to ship routing updates. RIP model 1 and IGRP each broadcast their updates.
Multicasting will get a bit extra sophisticated as you go out of your CCNA to the CCNP and CCIE, however by merely understanding what multicasting is, you go a good distance towards securing the CCNA.