In case when When the packet's destination MAC-address is unknown for the switch (not included in its routing table), the device unit sends this packet to all hosts of the network, except for the sender interface.
This phenomenon is called "unicast-flood". The most common reasons of unicast-flood are:
- Switch address table overflow (a common problem in large networks);
- Hosts with ARP timers greater than the address cache timeout;
- Incorrect STP settings.
InfiNet Wireless devices units 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:
| Center | |||||
|---|---|---|---|---|---|
|
R5000 device unit sends a packet with an unknown MAC-address to all ports until it receives a response with the packet which contains this address as the sender. After this the device unit will "learn" (i.e., it will add the unit adds the MAC-address to its address table and reserve it for reserves this MAC-address for the port where it has been was received). If the device unit can't learn in 4 seconds, and packets are still arriving, 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 unit statistics graphs:
| Center | |||||
|---|---|---|---|---|---|
|
Also, unicast-flooding can be detected in the "Switch Statistics" section of the "Device unit Status" tab:
| Center | |||||
|---|---|---|---|---|---|
|
R5000 devices units react in a similar manner to unidirectional traffic, which is not a unicast-flood. 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 without protection filter by checking the appropriate box in the settings (see above).