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Configuration of Unregistered Multicast on 200/300 Series Managed Switches

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Sat, 07/09/2016 - 16:00
Apr 26th, 2016
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Article ID: 1036

Objective

Internet Group Management Protocol (IGMP) is a protocol designed for multicast purposes. With IGMP, you can establish group memberships between different users within a network. IGMP is mainly used for multimedia streaming, such as video-chat, between different users (one-to-many users or many-to-many users) in a network. Snooping, on the other hand, is the term used when a third party in a communication listens or observes the current connection data traffic. Therefore, IGMP Snooping is a process that listens specifically to multicast traffic. By default, the 300 Series Managed Switches forwards all multicast frames to all the ports that are assigned to a specific VLAN. This behavior is insecure and the multicast frames could end up in the wrong place. You can enable IGMP Snooping to forward multicast traffic to only already registered multicast clients on specific ports of the switch. This way, the multicast frames are only forwarded to a specific multicast client within a VLAN instead of to all the users in that VLAN.

The objective of this document is to show you how to configure IGMP Snooping on 200/300 Series Managed Switches.

Applicable Devices

• SF/SG 200 and SF/SG 300 Series Managed Switches

Software Version

• 1.3.0.62

Enable Bridge Multicast

In order for IGMP snooping to work, bridge multicast must be enabled.

Step 1. Log in to the web configuration utility and choose Multicast > Properties. The Properties page opens:

Step 2. In the Bridge Multicast Filtering Status field, check the Enable check box.

Step 3. Click Apply.

Note: For information about how to configure multicast properties, refer to the article Multicast Properties Configuration on 300 Series Managed Switches.

Configure IGMP Snooping on a VLAN

Configure IGMP Snooping on a Single VLAN

Step 1. Log in to the web configuration utility and choose Multicast > IGMP Snooping. The IGMP Snooping page opens:

Step 2. Check Enable to start IGMP Snooping globally.

 

Step 3. Click Apply.

Step 4. Click the radio button that corresponds to the VLAN on which you would like to apply IGMP Snooping.

Step 5. Click Edit.

The Edit IGMP Snooping window appears.

Step 6. In the IGMP Snooping Status field, check the Enable check box. This option monitors the traffic to determine which hosts requested multicast traffic.

Step 7. In the MRouter Ports Auto Learn field, check the Enable check box. This option automatically learns to which the specific ports the MRouter is connected. An MRouter is a router designed to properly route multicast packets.

Step 8. In the Query Robustness field, enter the number queries the switch performs to connect to a host. If no response is received, the switch deletes the host information.

Step 9. In the Query Interval field, enter the time interval between sent query messages.

Step 10.  In the Query Max Response Interval field, enter the time in seconds a host is given to respond a query.

Step 11. In the Last Member Query Counter field, click one of the following:

• Use Default — This option uses the default number of IGMP Group-Specific queries to be sent before the switch assumes there are not any more members in the group.

• User Defined — This option lets you enter a specific number of IGMP Group-Specific queries to be sent before the switch assumes there are not any more members in the group.

Step 12. In the Last Member Query Interval field, enter the Maximum Response Delay used in case the switch cannot read the Max Response Interval value from group-specific queries.

Step 13. In the Immediate Leave field, check the Enable check box to block a multicast stream faster that was sent to a member port in the case that an IGMP Group Leave message is received.

Step 14. In the IGMP Querier Status field, check the Enable check box to enable IGMP Querier.

Step 15. In the Administrative Querier Source IP Address field, click one of the following radio buttons:

• Auto — This option chooses the management IP address.

• User Defined — This option lets you choose an IP address of your choice from the drop-down list.

Step 16. In the IGMP Querier Version field, click IGMPV3 if in this VLAN there are switches or multicast routers that perform source-specific IP multicast forwarding; otherwise, click IGMPV2.

Note: The information on the right side of the Edit IGMP Snooping window displays the current IGMP configuration. 

The following information is displayed:

• Operational IGMP Status — Current IGMP status of the chosen VLAN.

• Operational Query Robustness — Current Query Robustness value of the chosen VLAN.

• Operational Query Interval — Current Query Interval value of the chosen VLAN.

• Operational Query Max Response Interval — Current Query Max Response Interval value of the chosen VLAN.

• Operational Last Member Response Interval — Last Member Response Interval value of the chosen VLAN.

• Operational Last Member Query Counter — Last Member Query Counter value of the chosen VLAN.

• Operational Last Member Query Interval —  Last Member Query Interval value of the chosen VLAN.

• Operational Querier Source IP Address — Current Querier Source IP Address of the chosen VLAN.

Step 17. Click Apply.

Configure IGMP Snooping on Multiple VLANs

This section explains how to apply the IGMP snooping configuration of a specific VLAN, in multiple VLANs.

Step 1. Log in to the web configuration utility and choose Multicast > IGMP Snooping. The IGMP Snooping page opens:

Step 2. Click the VLAN with the IGMP snooping configuration that you want to apply on other VLANs.

Step 3. Click Copy Settings. The Copy Settings window appears.

Step 4. In the field provided, enter the VLANs to which you want to apply the IGMP snooping configuration of the previously chosen VLAN. You can enter each VLAN or a range of VLANs based on their entry number from the IGMP Snooping Table, such as 1, 2 or 1-2, or with their VLAN ID, such as VLAN1, VLAN2 or VLAN1-VLAN2.

Step 5. Click Apply.

Loading.
Chris Weir Mon, 05/02/2016 - 04:31
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I see that you are recommending that immeditate leave should be enabled although the IGMP querier is shown as v2.  In other Cisco documentation, there is a warning that immediate leave should not be enabled when using IGMP v2 if there might be multiple clients on a port.

e.g. http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960/software/... states:

"When using IGMPv2 snooping, use immediate-leave processing only on VLANs where just one host is connected to each interface. If immediate-leave processing is enabled on VLANs where multiple hosts are connected to an interface, some hosts might be dropped inadvertently."

Does this also apply to the sg300 switches, or do they have some way of detecting a cascaded port and automatically disabling immediate leave for that port?

Since finding the above quoted Cisco advice, I have been busy returning all my Cisco sg300 switches to the default state where immediate leave is disabled (we are using IGMP v2.)  Is this unnecessary, or would you recommend leaving immediate leave disabled when using IGMP v2?


Chris.

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