Brocade Communications Systems IPMC5000PEF Manual De Usuario
membership information by processing the IGMP reports and leave messages, so traffic can be
forwarded to ports receiving IGMP reports.
forwarded to ports receiving IGMP reports.
An IPv4 multicast address is a destination address in the range of 224.0.0.0 to 239.255.255.255.
Addresses of 224.0.0.X are reserved. Because packets destined for these addresses may require
VLAN flooding, devices do not snoop in the reserved range. Data packets destined to addresses in the
reserved range are flooded to the entire VLAN by hardware, and mirrored to the CPU. Multicast data
packets destined for the non-reserved range of addresses are snooped. A client must send IGMP
reports in order to receive traffic.
Addresses of 224.0.0.X are reserved. Because packets destined for these addresses may require
VLAN flooding, devices do not snoop in the reserved range. Data packets destined to addresses in the
reserved range are flooded to the entire VLAN by hardware, and mirrored to the CPU. Multicast data
packets destined for the non-reserved range of addresses are snooped. A client must send IGMP
reports in order to receive traffic.
An IGMP device's responsibility is to broadcast general queries periodically, and to send group queries
when receiving a leave message, to confirm that none of the clients on the port still want specific traffic
before removing the traffic from the port. IGMP V2 lets clients specify what group (destination address)
will receive the traffic but not to specify the source of the traffic. IGMP V3 is for source-specific
multicast traffic, adding the capability for clients to INCLUDE or EXCLUDE specific traffic sources. An
IGMP V3 device port state could be INCLUDE or EXCLUDE, and there are different types of group
records for client reports.
when receiving a leave message, to confirm that none of the clients on the port still want specific traffic
before removing the traffic from the port. IGMP V2 lets clients specify what group (destination address)
will receive the traffic but not to specify the source of the traffic. IGMP V3 is for source-specific
multicast traffic, adding the capability for clients to INCLUDE or EXCLUDE specific traffic sources. An
IGMP V3 device port state could be INCLUDE or EXCLUDE, and there are different types of group
records for client reports.
The interfaces respond to general or group queries by sending a membership report that contains one
or more of the following records associated with a specific group:
or more of the following records associated with a specific group:
•
Current-state record that indicates from which sources the interface wants to receive and not
receive traffic. This record contains the source address of interfaces and whether or not traffic will
be included (IS_IN) or not excluded (IS_EX) from this source.
receive traffic. This record contains the source address of interfaces and whether or not traffic will
be included (IS_IN) or not excluded (IS_EX) from this source.
•
Filter-mode-change record. If the interface state changes from IS_IN to IS_EX, a TO_EX record is
included in the membership report. Likewise, if the interface state changes from IS_EX to IS_IN, a
TO_IN record appears in the membership report.
included in the membership report. Likewise, if the interface state changes from IS_EX to IS_IN, a
TO_IN record appears in the membership report.
•
An IGMP V2 leave report is equivalent to a TO_IN (empty) record in IGMP V3. This record means
that no traffic from this group will be received regardless of the source.
that no traffic from this group will be received regardless of the source.
•
An IGMP V2 group report is equivalent to an IS_EX (empty) record in IGMP V3. This record
means that all traffic from this group will be received regardless of source.
means that all traffic from this group will be received regardless of source.
•
Source-list-change record. If the interface wants to add or remove traffic sources from its
membership report, the report can contain an ALLOW record, which includes a list of new sources
from which the interface wishes to receive traffic. It can also contain a BLOCK record, which lists
the current traffic sources from which the interface wants to stop receiving traffic.
membership report, the report can contain an ALLOW record, which includes a list of new sources
from which the interface wishes to receive traffic. It can also contain a BLOCK record, which lists
the current traffic sources from which the interface wants to stop receiving traffic.
IGMP protocols provide a method for clients and a device to exchange messages, and let the device
build a database indicating which port wants what traffic. The protocols do not specify forwarding
methods. They require IGMP snooping or multicast protocols such as PIM to handle packet
forwarding. PIM can route multicast packets within and outside a VLAN, while IGMP snooping can
switch packets only within a VLAN.
build a database indicating which port wants what traffic. The protocols do not specify forwarding
methods. They require IGMP snooping or multicast protocols such as PIM to handle packet
forwarding. PIM can route multicast packets within and outside a VLAN, while IGMP snooping can
switch packets only within a VLAN.
If a VLAN is not IGMP snooping-enabled, it floods multicast data and control packets to the entire
VLAN in hardware. When snooping is enabled, IGMP packets are trapped to the CPU. Data packets
are mirrored to the CPU in addition to being VLAN flooded. The CPU then installs hardware resources,
so that subsequent data packets can be switched to desired ports in hardware without going to the
CPU. If there is no client report or port to queriers for a data stream, the hardware resource drops it.
VLAN in hardware. When snooping is enabled, IGMP packets are trapped to the CPU. Data packets
are mirrored to the CPU in addition to being VLAN flooded. The CPU then installs hardware resources,
so that subsequent data packets can be switched to desired ports in hardware without going to the
CPU. If there is no client report or port to queriers for a data stream, the hardware resource drops it.
Queriers and non-queriers
An IGMP snooping-enabled Brocade device can be configured as a querier (active) or non-querier
(passive). An IGMP querier sends queries; a non-querier listens for IGMP queries and forwards them
to the entire VLAN. VLANs can be independently configured to be queriers or non-queriers. If a VLAN
has a connection to a PIM-enabled port on another router, the VLAN must be configured as a non-
querier. When multiple IGMP snooping devices are connected together, and there is no connection to
a PIM-enabled port, one of the devices must be configured as a querier. If multiple devices are
configured as queriers, after these devices exchange queries, then all except the winner stop sending
queries. The device with the lowest address becomes the querier. Although the system will work when
(passive). An IGMP querier sends queries; a non-querier listens for IGMP queries and forwards them
to the entire VLAN. VLANs can be independently configured to be queriers or non-queriers. If a VLAN
has a connection to a PIM-enabled port on another router, the VLAN must be configured as a non-
querier. When multiple IGMP snooping devices are connected together, and there is no connection to
a PIM-enabled port, one of the devices must be configured as a querier. If multiple devices are
configured as queriers, after these devices exchange queries, then all except the winner stop sending
queries. The device with the lowest address becomes the querier. Although the system will work when
Queriers and non-queriers
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FastIron Ethernet Switch IP Multicast Configuration Guide
53-1003085-02