Implement and Troubleshoot IGMP

Specifies how a host can register with a router in order to receive specific multicast traffic

•  To inform a local multicast router that a host wants to receive multicast traffic for a specific group
•  To inform local multicast routers that a host wants to leave a multicast group (in other words, the host is no longer interested in receiving the multicast group traffic)

 

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IGMPv1

RFC 1112

• Membership reports are issued by hosts that want to receive a specific group (GDA)
• Membership queries are issued by routers at regular intervals to check whether there is a host interested in the GDA
• Host membership reports are issued either unsolicited or in response to a membership query
• Membership queries are sent by routers to all multicast address
  • 224.0.0.1
    • All multicast capable hosts
  • Host for each group must respond to the query or the router will stop forwarding all traffic for that GDA after 3 attempts
• IGMPv1 has no leave mechanism

Default Query Interval – 60 Seconds

 

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IGMPv2

RFC 2236

• Host should send a leave message to destination 224.0.0.2
  • All multicast capable routers

 

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IGMPv3

RFC 3376

• Backwards compatible with v1 and v2
  • V1 membership report
  • V2 membership report and leave group
• Source Specific Multicast (SSM)

 

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IGMP Snooping

• Allows switch to listen to IGMP conversations between host and router
• When switch hears an report for host to multicast group it adds a host port number to the GDA list
• When it hears a IGMP leave it removed the hosts port from the CAM table entry
• Learning Router Port
  • IGMP Membership query send to 01-00-5e-00-00-01
  • PIMv1 hello send to 01-00-5e-00-00-02
  • PIMv2 hello send to 01-00-5e-00-00-0d
  • DVMRP probes send to 01-00-5e-00-04
  • MOSPF message send to 01-00-5e-00-05 or 06

Enabled on per-VLAN basis

 

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IGMP Querier

Sends periodic IGMP queries that trigger IGMP report messages from hosts that want to receive IP multicast traffic

 

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IGMP Proxy

Enables hosts in undirectional link routing (UDLP) environment tha are not directly connected to a downstream router to join a multicast group sources from an upstream network

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https://www.safaribooksonline.com/library/view/ccie-routing-and/9780133590890/ch07lev2sec5.html

https://supportforums.cisco.com/discussion/11211866/what-are-differences-between-igmp-version-1-2-3-multicast