Igmp snooping v3
These two features can achieve the same goal: reduce traffic replication and save air time. The controller maintains a mapping table and forwards multicast traffic only to the hosts that have joined the specific multicast group.
In both cases, user VLANs must be trunked to the uplink router. This connection ensures that the router can receive and process the IGMP messages. Welcome Back! Select your Aruba account from the following: Aruba Central Login to your cloud management instance. Partner Ready for Networking Login to access partner sales tools and resources. Airheads Community Login to connect, learn, and engage with other peers and experts.
AnandKumar Sukumar Aruba Employee. The controller uses this information to build a multicast forwarding table that defines mapping of a particular multicast group, tunnels, and outgoing port s or interface s that have active members subscribed to the multicast traffic stream.
IGMP proxy: The controller joins multicast group s on behalf of mobile clients. This action reduces the number of IGMP messages and also addresses the mobility issues, because the controller is aware of the client roaming and the new VLAN. Only IGMP v1 and v2 are supported. Version history. Revision :. Last update:. Updated by:. AnandKumar Sukumar.
View article history. Labels 1.Participate in the Technical Documentation Ideas forum. Multicast traffic addressed to a unicast cluster IP address is forwarded to the last-hop router that is configured with the shared multicast MAC address. To support cluster-addressed multicast traffic, assign a static multicast MAC address for the destination IP address of the end host or cluster. Note Changing the lookup mode is disruptive. Multicast forwarding is not optimal until all multicast entries are programmed with the new lookup mode.
Also, if 32 IP addresses are mapped to a single MAC address, forwarding on the device might be suboptimal. Hosts join multicast groups either by sending an unsolicited IGMP join message or by sending an IGMP join message in response to a general query from a multicast router the switch forwards general queries from multicast routers to all ports in a VLAN. When other hosts that are interested in this multicast traffic send IGMP join requests, the switch adds them to the existing Layer 2 forwarding table entry.
IGMP snooping suppresses all but one of the host join messages per multicast group and forwards this one join message to the multicast router. The switch forwards multicast traffic for the multicast group specified in the join message to the interfaces where join messages were received see Figure Layer 2 multicast groups learned through IGMP snooping are dynamic.
However, you can statically configure Layer 2 multicast groups using the mac address-table static command. When you specify group membership for a multicast group address statically, the static setting supersedes any IGMP snooping learning. Multicast group membership lists can consist of both static and IGMP snooping-learned settings. Multicast router A sends a general query to the switch, which forwards the query to ports 2 through 5 all members of the same VLAN.
Host 1 wants to join multicast group Using IP-based forwarding can avoid group address aliasing problem and optimize per group or per group and source forwarding. The switch engine matches on the destination IP address of multicast data packets. If they are If MAC-based is configured, the entry is as follows.
In this case, the switch engine matches on the destination MAC address of the packets. The packets with If another host for example, Host 4 sends an unsolicited IGMP join message for the same group Figurethe CPU receives that message and adds the port number of Host 4 to the forwarding table. Any known multicast traffic is forwarded to the group and not to the CPU.
Interested hosts must continue to respond to the periodic general IGMP queries. When IGMP snooping receives a group-specific IGMPv2 leave message from a host, it sends out a MAC-based general query to determine if any other devices connected to that interface are interested in traffic for the specific multicast group. If IGMP snooping does not receive an IGMP Join message in response to the general query, it assumes that no other devices connected to the interface are interested in receiving traffic for this multicast group, and it removes the interface from its Layer 2 forwarding table entry for that multicast group.
If the leave message was from the only remaining interface with hosts interested in the group and IGMP snooping does not receive an IGMP Join in response to the general query, it removes the group entry and relays the IGMP leave to the multicast router.
Upon receiving a group-specific IGMPv2 leave message, IGMP snooping immediately removes the interface from the Layer 2 forwarding table entry for that multicast group, unless a multicast router was learned on the port. Immediate-leave processing improves bandwidth management for all hosts on a switched network. Immediate-leave processing is supported only with IGMP version 2 and 3 hosts. IGMPv3 uses source-based filtering, which enables hosts and routers to specify which source addresses should be allowed or blocked for a specific multicast group.
When you enable IGMPv3 snooping, the switch maintains IGMPv3 states based on messages it receives for a particular group in a particular VLAN and either allows or blocks traffic based on the following information in these messages:. When a host wants to receives multicast traffic only from specific sources, it can send IGMPv3 joins with source filtering. The second entry constrain group traffic from source The first entry drops group traffic from any other sources since there is no receiver interesting in other sources.
IGMPv3 immediate-leave processing is active if explicit-host tracking is enabled.The IGMPv1 was the first widely used version of the protocol that allowed a station to explicitly announce its willingness to receive a particular multicast traffic. This version had two messages only: the Membership Query and a Membership Reply. The Membership Query was always sent to There was no message to announce that a station is leaving unsubscribing a multicast group, resulting in situations that a multicast stream was fed to a segment even after all stations have left the particular group.
Only after a timeout period the router discovered that there are no more subscribers to the group, and stopped the multicast feed. IGMPv2 brought a number of improvements. First, it allows the Membership Query to be both general sent to The general Membership Query is used to find out all multicast groups that the stations are subscribed to.
The group-specific Membership Query is used to find out if there is a subscriber for a particular group. Second, there was a new message introduced in IGMPv2 - the Leave message to advertise that a station is unsubscribing from a multicast group, allowing the router to stop an unnecessary multicast stream feed much more promptly. Third, the IGMPv2 cleared the way how a multicast querier a router that send Queries is elected if there are multiple multicast routers connected to a common network.
Other routers are free to listen to the Replies they have to do it anyway but they do not send Queries themselves. Both IGMPv1 and IGMPv2 are suitable for any source multicast where a station is interested in receiving all transmissions to a multicast group, regardless of who is the sender. However, there are applications where a station wants to receive only a transmission from a particular sender to a particular group.
We call this multicast the source-specific multicast. The extensions of the IGMP to support the source-specific multicast led to creation of the IGMPv3 that has more complex inner working than its predecessors, and its main difference is the support of source-specific multicast.We recommend that you do not disable IGMP snooping on the device.
If you disable IGMP snooping, you might see reduced multicast performance because of excessive false flooding within the device.
Configuring IGMP Snooping on Switches
The IGMP snooping software responds to topology change notifications. By default, IGMP snooping is enabled on the device. Source filtering that allows forwarding of multicast packets based on destination and source IP addresses. Multicast forwarding alternately based on the MAC address.
Both IGMPv1 and IGMPv2 support membership report suppression, which means that if two hosts on the same subnet want to receive multicast data for the same group, the host that receives a member report from the other host suppresses sending its report. Membership report suppression occurs for hosts that share a port. The fast leave feature does not send last member query messages to hosts. As soon as the software receives an IGMP leave message, the software stops forwarding multicast data to that port.
IGMPv1 does not provide an explicit IGMP leave message, so the software must rely on the membership message timeout to indicate that no hosts remain that want to receive multicast data for a particular group. The software ignores the configuration of the last member query interval when you enable the fast leave feature because it does not check for remaining hosts.
This source-based filtering enables the device to constrain multicast traffic to a set of ports based on the source that sends traffic to the multicast group. By default, the software tracks hosts on each VLAN port.
IGMP snooping v3
The explicit tracking feature provides a fast leave mechanism. Because every IGMPv3 host sends membership reports, report suppression limits the amount of traffic that the device sends to other multicast-capable routers.
The proxy feature builds the group state from membership reports from the downstream hosts and generates membership reports in response to queries from upstream queriers. Even though the IGMPv3 membership reports provide a full accounting of group members on a LAN segment, when the last host leaves, the software sends a membership query.
You can configure the parameter last member query interval. If no host responds before the timeout, the software removes the group state. When PIM is not enabled on an interface because the multicast traffic does not need to be routed, you must configure an IGMP snooping querier to send membership queries.
You define the querier in a VLAN that contains multicast sources and receivers but no other active querier. Querier election occurs in the following configurations:. When there are multiple switch queriers configured with the same subnet on the same VLAN on different switches. When the configured switch querier is in the same subnet as with other Layer 3 SVI queriers.Configure the VLAN in global configuration mode.
When administratively enabled, the IGMP snooping querier moves to the nonquerier state if it detects the presence of a multicast router in the network.
Catalyst 6500 Release 12.2SY Software Configuration Guide
When it is administratively enabled, the IGMP snooping querier moves to the operationally disabled state under these conditions:. The following are the restrictions for IGMP snooping:.
The switch supports homogeneous stacking and mixed stacking. Mixed stacking is supported only with the Catalyst S switches. A homogenous stack can have up to eight stack members, while a mixed stack can have up to four stack members. All switches in a switch stack must be running the LAN Base image. This feature is not supported when the query includes IGMPv3 reports. IGMP version 2 is the default version for the device.
The actual leave latency in the network is usually the configured leave time. However, the leave time might vary around the configured time, depending on real-time CPU load conditions, network delays and the amount of traffic sent through the interface.
You can use ip igmp max-groups action replace interface configuration command on a logical EtherChannel interface but cannot use it on ports that belong to an EtherChannel port group. If you configure the throttling action and set the maximum group limitation after an interface has added multicast entries to the forwarding table, the forwarding-table entries are either aged out or removed, depending on the throttling action.
Only Layer 2 ports participate in MVR. You must configure ports as MVR receiver ports. Receiver ports can only be access ports; they cannot be trunk ports. The maximum number of multicast entries MVR group addresses that can be configured on a device that is, the maximum number of television channels that can be received is MVR is not supported when multicast routing is enabled on a device.
If you enable multicast routing and a multicast routing protocol while MVR is enabled, MVR is disabled, and you receive a warning message. If you try to enable MVR while multicast routing and a multicast routing protocol are enabled, the operation to enable MVR is cancelled, and you receive an error message.
When the device receives an IGMP report from a host for a particular multicast group, the device adds the host port number to the forwarding table entry; when it receives an IGMP Leave Group message from a host, it removes the host port from the table entry.
It also periodically deletes entries if it does not receive IGMP membership reports from the multicast clients. The multicast router sends out periodic general queries to all VLANs. All hosts interested in this multicast traffic send join requests and are added to the forwarding table entry.
Because the device uses IP multicast groups, there are no address aliasing issues. If you specify group membership for a multicast group address statically, your setting supersedes any automatic manipulation by IGMP snooping. Multicast group membership lists can consist of both user-defined and IGMP snooping-learned settings. You can configure an IGMP snooping querier to support IGMP snooping in subnets without multicast interfaces because the multicast traffic does not need to be routed.
These versions are interoperable on the device.When there are multiple receivers on the network then using multicast traffic sounds like a good idea. Routers use PIM Protocol Independent Multicast to figure out where to forward multicast traffic but what about switches? Layer two switches are simple devices. When a frame arrives, they check for the destination MAC address, perform a lookup in the MAC address table and then forward the frame.
Take a look at the example below:. Above we have a video server that is streaming multicast traffic to destination When the switch receives this traffic then it will do a lookup for MAC address Since this MAC address has never been used as a source, all multicast traffic will be flooded.
All hosts will receive our traffic whether they want it or not. IGMP snooping allows us to constrain our multicast traffic. As the name implies, this is done by listening to IGMP traffic between the router and hosts:. What do we do when we use IGMP version 1? Above we have a multicast enabled router, a switch and three host devices.
We are using a cheap budget switch that is only able to look at layer two Ethernet frames. It does have support for IGMP snooping though.
Above you can see that one of our hosts H1 sends a membership report for multicast group Our switch has no idea where to forward this to so the first time it will flood it on all interfaces, including the internal interface to the CPU.
The interfaces that were added are for H1, R1 and the internal interface. Why did the switch add the interface of the router in the CAM table? Once IGMP snooping is enabled, the switch will detect multicast enabled routers and it does so by listening to the following messages:.
Please turn it on for the best experience. IPTV service consists of three entities-multicast source, client device and multicast network. And give you the corresponding suggested configuration guide. As illustrated in the topology above, Internet Gateway Router is connected to the L2 switch via port 1. If the desktop computer is also to receive the multicast service, Just Enable port 5. Note: Port 5 is not going to receive any multicast data, so port 5 is not in the multicast table list.
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How to configure IGMP Snooping for IPTV network using L2 switch?
Configuration Guidance: As illustrated in the topology above, Internet Gateway Router is connected to the L2 switch via port 1. Is this faq useful? Your feedback helps improve this site. Yes Somewhat No. Submit No, Thanks. Thank you We appreciate your feedback. Click here to contact TP-Link technical support. Subscribe TP-Link takes your privacy seriously.
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