Lecture 2 - IP Multicast Routers and Routing Protocols

This is the second video of a complete lecture series on IP Multicast and its implementation on both IOS and Junos routers with a focus on CCIE and JNCIE candidate requirements.
In this lecture, we discuss the following topics:
How IP mutlicast routers think about forwarding of IP multicast packets (away from a source vs. towards a destination) and how is it important for the CCIE and JNCIE
How an IP multicast router builds the multicast forwarding database
The concept of upstream vs downstream interfaces (IIF vs OIL) in the multicast FIB
Major responsibilities of a multicast routing protocol such as PIM, DVMRP etc.
How an IP multicast routing protocol populates the multicast routing table
How an IP multicast router uses the multicast FIB to forward packets in the data plane
(S,G) vs. (*,G) in IP multicast
What is a reverse path forwarding or RPF check
How an IP multicast router performs the RPF check to control multicast loops
How an IP multicast router uses the unicast routing table to perform RPF checks on multicast packets

[@Openwrt2023]

This is by far the best lecture for IP multicast. Thank you.

[@kamalzafar6896]

The whole series is so professionally done! Amazing. Great work man. Very hard to find any training better than this, even in paid ones.

[@dense2461]

Gosh, this "guiding towards a destination" vs "guiding away from a source" comparison, in the beginning, is amazing!

[@alaeddingabsi3660]

Decoding packets is the master of Multicast of all time :-) Thank you very much for your time and for these great videos. Best video on the subject of Multicast ever. Great presentation skills as well.

[@camerafloss]

Very well done, the technology and operational issues were well balanced and very informative.

[@syrilthomas6400]

Good quality tutorials 👌

[@alexandermedina4950]

How come I just found this video series? Thank you for this!

[@bestsaurabh]

Thank you so much for the multicast deep dive tutorial.

[@DecodingPackets]

Thank you for your kind words. I am glad you are finding the content useful.

[@manedirajesh2173]

very well explained , great tutorials

[@Vrbik15]

omg what a good tutorials I need more time to see them all'!

[@richarani4940]

well explained. Thank you !! :)

[@PETAJOULE543]

RPF in detail. Basically, each multicast group member has only one IIF where they only accept incoming multicast packets. This greatly reduces 'multicast storms/loops'. (=Multicast routing table for each group member contains one IIF and multiple outgoing.) Also, each member has the same multicast group IP address (raw address without subnets). So with this one particular IP address the message goes to each group members, once. Also few things about multicast trees that can either be PIM-DM (source known) or PIM-DM ('shared tree'). The tree structure ensures loop-free routing and basically RPF is one of its cause.

[@claudiuargeseanu1952]

1. throughout the video you've talked about multicast routing protocol building the multicast routing table. Is it possible to configure manual multicast routes? say the source, the group, the iif and the oil? 2. what happens if you have a (*,G) IIF, OIL route and the router receives packets towards that group on two different interfaces from two different sources?

[@biswajit007-4Ever]

Excellent !!

[@DecodingPackets]

Thank you. I am glad you are finding the content useful.

[@juanjo11394]

At 18:00, I think it should say "Identify downstream interface or IIF" as the router would be receiving multicast traffic from the source, while second bullet should say "Identify upstream interfaces or OIL" as the router would be transmitting multicast traffic to receivers interested in multicast traffic for a certain group, right? I mean, it would be fine as it is shown in the slide from the source and destination endpoints perspective but not from the router's, right?

[@jenea949]

Thank you for this video!

[@ashwindv357]

Thanks for this amazing multicast series. Can you share slides of this series?

[@manedirajesh2173]

what happens if we have multiple paths from IGP , how do RPF respond

[@danielwerner6184]

What happened at 19:24 ? :D

[@ihtishamhussain9216]

thanks a lot sir

[@gamygym]

thx

[@DecodingPackets]

You are very welcome.

[@DecodingPackets]

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