Paradyne BitStorm 2400, User Manual

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1. BitStorm 2400 Overview
2400-A2-GB20-10 December 2002
1-13
IGMP V2 Operation
IGMP V2 enhances the IGMP V1 standard by adding explicit messages to allow a
host to signal that it is leaving a multicast group and a message for a router to
query for hosts interested in a specific group. IGMP V2 join operations operate as
they did in IGMP V1. When a host no longer has interest in a multicast group, the
host V2 host will issue an IGMP Leave Message for that group. The message is
addressed to the all-routers group (224.0.0.2).
Routers receiving a Leave Group message will typically issue a Group Specific
Query message to the interface on which it received the Leave Group message.
The purpose of this Query is to determine if there are any other hosts remaining
on this interface that still have interest in this group.
IGMP V1 and V2 Co-existence
If a Router or IGMP Snooping switch detect a host on an interface using the IGMP
V1 report messages, the router must assume that there is at least one IGMP
V1-only host on that interface and revert to the IGMP V1 mode of operation on that
interface.
Summary of IGMP V2 Message Formats
Table 1-2, Messages , summarizes the types of messages that the IGMP Router,
proxy, or Snooping agent must listen for and respond to every 10 seconds.
See the IETF Standard documentation for complete packet layout and formatting
rules.
Table 1-2. Messages
Message Source IP @ Destination IP @
IP Header
Protocol IGMP V2
Type IGMP V2
Max Resp IGMP V2
Group @
Membership
Report Host IP @ MC Group
being reported 0x02 0x12 0 MC Group being
Reported
Leave Group Host IP @ All Routers
224.0.0.2 0x02 0x17 0 MC Group being
left
General Query Querier’s IP @ All Hosts
224.0.0.1 0x02 0x11 100 0
Group Specific
Query Querier’s IP @ All Hosts
224.0.0.1 0x02 0x11 100 MC Group being
queried