16/24-Port PoE Switch
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Figure 6-35
6.8 IGMP Snooping
IGMP Snooping (Internet Group Management Protocol Snooping) is operated on the layer
two device, it is to generate layer two multicast forwarding table via snooping the IGMP
packet between layer three device and host, which is to manage and control the forwarding
of multicast data packet and realize layer two required distribution of multicast data packet.
6.8.1 IGMP Snooping Theory
Operating layer two device of IGMP Snooping can establish mapping relation for port and
MAC multicast address via analysis upon received IGMP packet, and it is to forward multicast
data according to the mapping relation.
The multicast data will be broadcasted in the layer two network when the layer two device
doesn't operate IGMP Snooping; after layer two device operates IGMP Snooping, the known
multicast data of multicast group will not be broadcasted in the layer two network but
multicasted to designated receivers.
IGMP Snooping can only forward the information to the needed receivers via layer two
multicast, which can bring following advantages:
• Reduce broadcast packet in the layer two network, save network bandwidth;
• Enhance security of multicast information;
• Bring convenience for realizing individual billing for each host.
Figure 6-36
The IGMP Snooping config interface is shown in Figure 6-36.
• IGMP Snooping: enable or disable IGMP Snooping function.
• IGMP Leave Packet: enable or disable the function of quick leave.
7.1 PoE Settings
Power over Ethernet (PoE) means the device uses the Ethernet port to provide power to the
device via the twisted pair cable remotely. The PoE function realizes the centralized power
supplying and easy to backup. The network terminal just uses one simple network cable
without external power source. It complies the IEEE 802.3af and IEEE 802.3at and adopts
the universal recognized power port. It is for the IP camera, IP phone, wireless access point
(wireless AP), portable device recharger, POS, data acquisition and etc.
Refer to Figure 7-1 for PoE system. It includes PoE power, Power Sourcing Equipment(PSE),
power interface (Pl) and powered device (PD).
Pl)
Pl)
Pl)
Figure 7-1
1. PoE power
PoE is to provide power to the whole system.
2. PSE
PSE is to provide power to the PD directly. The PSE supports the functions such as search,
detect PD, categorize PD, and provide power to it, realize power consumption management,
check the PD connection and etc.
3. Pl
Pl refers to the Ethernet interface that has the PoE function. It is called PoE port. It includes
FE and GE.
The PoE remote power supplying has two modes:
• Over signal wires-The PSE uses the pairs (1, 2, 3, 6) for transmitting data in a category
3/5 twisted pair cable to supply DC power while transmitting data to PDs.
• Over spare wires-The PSE uses the pairs (4, 5, 7, 8) not transmitting data in a category
3/5 twisted pair cable to supply DC power to PDs.
