Network PC World

Multicast Overview Multicast is a network communication method that delivers a single stream from a source to multiple destinations. It optimizes network bandwidth usage, especially in applications like video conferencing, IPTV, and stock tickers. The Internet Group Management Protocol (IGMP) is used in Layer 2 networks, while Protocol Independent Multicast (PIM) handles Layer 3 communication. Technical Tip : Multicast is UDP-based, which lacks the reliability mechanisms of TCP, such as windowing and error correction, potentially leading to duplicate packets and out-of-order delivery. Multicast Addressing Multicast addresses are in the Class D range (224.0.0.0 to 239.255.255.255) . These addresses are not assigned to individual devices but represent groups. Well-known Multicast Address Types : Local network control block (224.0.0.0/24) : Protocol control traffic within a broadcast domain. Internetwork control block (224.0.1.0

Today, while working on a multicast lab on Cisco Router. I build a lab to send multicast stream from one end to other end via VLC. I found that, while checking router with " show ip mroute " command , receiver PC was successful registering with Rendezvous Point Server to receive required multicast traffic but the Multicast source (Sender) was not registering with RP. Upon a day's troubleshooting, i found in the packet capture that VLC Sender is sending multicast traffic with TTL Value 1, this is default behavior of VLC player and which will definitely be discarded by first receiving hop. So I have to increase the TTL value little higher so that the multicast packets can traverse to some hops and reach the receiver. To change the TTL value of the packet for sending multicast stream from VLC, you can change the default settings as per give below path and snap. I also tried this in GNS3 and was working fine. Go to Tools > Preferences >  Select ALL radio button