Table of Index
- What is IGMP Snooping?
- IGMP snooping without L3 devices
- IGMP Snooping on L3 Devices
- IGMP Group Leave
- Configuration of IGMP Snooping
- Global IGMP Snooping configuration:
- IGMP Snooping without L3 device:
- Example without Router
- Solution 1: IGMP snooping querier.
- Solution 2: PIM onSwitch Virtual interface
- Solution 3: Static mrouter port
- Solution 4: Static multicast entry
- Alternative solution: Disable IGMP snooping
- What is Cisco Group Management Protocol (CGMP)?
- What is CGMP Process?
This eBook is based on IP MULTICAST ROUTING that has been collected from different sources and people. For more information about this ebook. Kindly write to ummedsingh7427@gmail.com. I will happy to help you.
Copyright 2023 by Ummed Singh
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What is IGMP Snooping?
When there are multiple recipients connected to a network, utilizing multicast traffic is a favorable choice. It proves to be more efficient compared to unicast, as the traffic is transmitted only once, conserving valuable bandwidth. Moreover, it outperforms broadcast by ensuring that only the intended recipients who are interested in the traffic receive it. While routers employ Protocol Independent Multicast (PIM) to determine the appropriate path for forwarding multicast traffic, the role of switches in this process is different. Layer two switches are uncomplicated devices.
They learn the source MAC addresses and store them in their MAC address tables. Upon receiving a frame, they examine the destination MAC address, perform a lookup in the MAC address table, and then forward the frame accordingly. This mechanism functions effectively for unicast traffic. However, it poses a challenge when dealing with multicast traffic. Refer to the following example for further understanding:
In the given scenario, we have a video server that is transmitting multicast traffic to the destination address 239.1.1.1, which corresponds to the MAC address 0100.5e01.0101. When this traffic reaches the switch, it will perform a lookup for the MAC address 0100.5e01.0101. Since this MAC address has not been used as a source before, the switch will flood the multicast traffic. Consequently, all hosts connected to the switch will receive the traffic, regardless of whether they actually want it or not. To address this issue, IGMP snooping comes into play. IGMP snooping restricts the distribution of multicast traffic. It achieves this by monitoring the IGMP messages exchanged between the router and the hosts. Here's how it works: When a host sends a membership report for a multicast group, the switch adds an entry in its CAM (Content Addressable Memory) table, associating the multicast group with the interface connected to that host. When a host sends a leave group message for a multicast group, the switch removes the corresponding entry from its CAM table, indicating that the host is no longer interested in receiving traffic for that multicast group. However, things become a bit more complex when dealing with IGMP version 1 and scenarios where hosts don't send leave group messages. In IGMP version 1, hosts do not send explicit leave group messages, which means there's no IGMP traffic to snoop. Additionally, we need to consider situations where a video server only streams multicast traffic without actually joining any multicast groups. To address these challenges, we need to delve deeper into IGMP snooping.
IGMP snooping without L3 devices
Let's begin with a simple example. The following diagram will be used for illustration:
In the given setup, we have a multicast-enabled router, a switch, and three host devices. The switch has a CPU and a CAM table (MAC address table) connected to an internal interface called "INT." Although it is a budget switch with limited layer two frame analysis capabilities, it does support IGMP snooping. Let's explore what happens when IGMP snooping is enabled on this switch:
Impressum
Verlag: BookRix GmbH & Co. KG
Texte: Ummed Singh
Bildmaterialien: Uday Bhan Thakur
Cover: Lalit Rao
Lektorat: Ajay Sharma
Korrektorat: Anand Kumar
Übersetzung: Ummed Singh
Satz: Shivam Singh
Tag der Veröffentlichung: 16.07.2023
ISBN: 978-3-7554-4708-5
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Widmung:
the packet to all interested receivers.
Receivers interested in receiving multicast data join the multicast group by sending a membership request to the nearest router. The router adds the receiver to the multicast distribution tree, and subsequent multicast packets are forwarded to the receiver's interface.
Overall, IP multicast routing enables efficient one-to-many or many-to-many communication by minimizing network traffic and reducing processing overhead on both the sender and receivers. It is commonly used in applications such as video streaming, online gaming, and audio conferencing, where simultaneous delivery of data to multiple recipients is required.