Startup and functions
7966_en_04
PHOENIX CONTACT
3-5
3.2.2
Multi-address function
The switch learns all the source addresses for each port. Only packets with:
–
Unknown source addresses
–
A source address for this port
–
A multicast/broadcast address
in the destination address field are forwarded via the relevant port. The switch can learn up
to 4000 addresses. This is important when more than one termination device is connected
to one or more ports. In this way, several independent subnetworks can be connected to
one switch.
3.2.3
Learning addresses
The FL NAT SMN 8TX(-M) independently learns the addresses for termination devices,
which are connected via a port, by evaluating the source addresses in the data telegram.
When the switch receives a data telegram, it only forwards this data telegram to the port that
connects to the specified device (if the address could be learned beforehand).
The FL NAT SMN 8TX(-M) can learn up to 4000 addresses and store them in its table. The
switch monitors the age of the learned addresses. The switch automatically deletes from its
address table address entries that have exceeded a specific age (default: 40 seconds,
adjustable from 10 to 825 seconds, aging time).
3.2.4
Prioritization
The switch supports four priority queues (traffic classes according to IEEE 802.1D) for
adjusting the internal packet processing sequence. Data telegrams that are received are
assigned to these classes according to their priority, which is specified in the prioritization
tag:
–
Data packets with the value “0” or “1” in the priority field have the lowest priority (de-
fault).
–
Data packets with the value “2” or “3” in the priority field have the second lowest priority.
–
Data packets with values between “4” and “5” in the priority field have the second high-
est priority and are transmitted via the switch.
–
Data packets with values between “6” and “7” in the priority field have the highest prior-
ity and are transmitted via the switch.
All learned entries are deleted on a restart.
A link down deletes all the entries of the affected port.
A list of detected MAC addresses can be found in the MAC address table (see Section
““Diagnostics/Mac Address Table” menu” on page 4-29). The MAC address table can be
deleted via "Clear".
The aging time is set using the "dot1dTpAgingTime"
MIB object (OID 1.3.6.1.2.1.17.4.2). The available setting range is 10 - 825 seconds. For
static configuration, an aging time of 300 seconds is recommended.