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--- networking:igmp_snooping [2020/12/24 00:17] – peter
+++ networking:igmp_snooping [2020/12/24 00:42] (current) – peter
@@ Line 3: / Line 3: @@
 [[https://en.wikipedia.org/wiki/Multicast_routing|Multicast routing]] is a networking method for efficient distribution of one-to-many traffic.
-**IGMP** (Internet Group Management Protocol) snooping constrains the flooding of IPv4 multicast traffic on VLANs on a device.
+When your network has plenty of multicast traffic, the performance for the entire network can take a hit because of excessive false flooding.
-With IGMP snooping enabled, the device monitors IGMP traffic on the network and uses what it learns to forward multicast traffic to **only** the downstream interfaces that are connected to interested receivers.
+**IGMP** (Internet Group Management Protocol) snooping optimizes that performance overhead.
-The device conserves bandwidth by sending multicast traffic only to interfaces connected to devices that want to receive the traffic, instead of flooding the traffic to all the downstream interfaces in a VLAN.
+The Router decides which devices will receive the applicable multicast traffic to improve the overall network speed.
+  * It monitors IGMP traffic on the network and uses what it learns to forward multicast traffic to **only** the downstream interfaces that are connected to interested receivers.
+  * It conserves bandwidth by sending multicast traffic only to interfaces connected to devices that want to receive the traffic, instead of flooding the traffic to all the downstream interfaces.
+Without IGMP Querying/Snooping, Multicast traffic is treated in the same manner as a Broadcast transmission, which forwards packets to all ports on the network.
+IGMP Snooping generates no additional network traffic, which significantly reduces the Multicast traffic passing through your switch.
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 ===== Benefits of IGMP Snooping =====
-  * **Optimized bandwidth utilization**:  IGMP snooping’s main benefit is to reduce flooding of packets.  The device selectively forwards IPv4 multicast data to a list of ports that want to receive the data instead of flooding it to all ports in a VLAN.
+  * **Optimized bandwidth utilization**:  IGMP snooping reduces flooding of packets.  The device selectively forwards IPv4 multicast data to a list of ports that **want** to receive the data instead of flooding it to all ports in a VLAN.
   * **Improved security**:  Prevents denial of service attacks from unknown sources.
+----
+===== When to Enable IGMP Snooping for Home Use =====
+Enable IGMP when you frequently use any kind of streaming or mirroring from your devices to stream to IOT devices, such as Chromecast or Apple TV.
+Do not turn it on unless actually needed.  This will just add extra traffic, which the router will need to listen to and monitor; and could result in less performance.
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 [[https://tools.ietf.org/html/rfc3171|RFC 3171 - IANA Guidelines for IPv4 Multicast Address Assignments]]
+[[https://tools.ietf.org/html/rfc1112|RFC 1112 - IGMP Version 1]]
+[[https://tools.ietf.org/html/rfc2236|RFC 2236 - IGMP Version 2]].