In case
Unicast-flood occurs when the
packetunicast frame's destination MAC
-address is unknown for the switch (not included in its
routing tablerouting table),
the device it sends this
packet to frame to all
hosts interfaces of the network,
except for the besides the sender interface
.This phenomenon is called unicast-flood. The most common reasons of unicast-flood are:
- Switch address MAC address table overflow (a common problem in large networks);
- Hosts with ARP timers greater longer than the address cache timeout;ARP cache time on switches
- Incorrect STP settings
- Incorrect switch groups settings .
InfiNet Wireless devices provide unicast-flood protection. In this case, you can allow unlimited unicast-flood without protection filter by setting the check box in MAC Switch settings:
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| title | Figure - How to allow unicast-flood without protection filter |
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- (in particular, when the IDs of switch groups for the receiving and sending traffic are different).
The unicast-flood process on devices is the following: if the frame's destination MAC-address is not included in the unit's MAC switch forwarding table, then this frame is flooded to all interfaces besides the sender interface. The distribution occurs until the unit receives a frame with this MAC-address as the sender (i.e., the interface to which the frame was destinated to respond). After that, the device will learn: it will add this MAC address to the MAC switch forwarding table and map it with the interface from which it was received. If the device does not learn in 4 seconds, and packets are frames still arrivingarrive, then traffic to this direction will be blocked for 4 seconds. Then the process repeats.
This process has the following representation in the graphs, for example, in the device statistics graphsunit's interfaces and links graphs:
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| title | Figure - Unicast-flood example in graphicsthe interfaces graphs |
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Also, unicast-flooding can be detected in the "Switch Statistics" section of the → "Device Status" tab in "Flood" column:
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| title | Figure - Unicast-flood detection in switch statistics |
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Infinet Wireless units provide unicast-flood protection. If necessary, you can allow unlimited unicast-flood without protection filter through the switch group by setting the check box in "Basic Settings" → "MAC Switch" settings:
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| title | Figure - How to allow unicast-flood without protection filter |
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Devices react to unidirectional traffic (which is not a unicast-flood) in a similar manner. This happens, for example, in case of generating "artificial" traffic (using specialized devices units or software) or when the real traffic is unidirectional. In these cases, it is recommended to allow unlimited unicast-flood through the switch group without protection filter by checking the appropriate box in the settings (see above)filter.