Dell PowerConnect B-FCXs, Configuration Manual

Page: 355 / 1494

PowerConnect B-Series FCX Configuration Guide 313
53-1002266-01
Flow-based MAC address learning
9
•
A source MAC address is learned only on the ingress (source) packet processor. The MAC
address is added to other packet processors as needed by their incoming traffic flows. During
a brief period until the destination MAC address is successfully added to the hardware MAC
table, unknown unicast flooding is expected on the VLAN.
•
When a flow-based MAC address moves, it is deleted from all of the packet processors, then
relearned on each packet processor individually, as needed by incoming traffic flows.
•
The software MAC address table in the CPU uses a hashing algorithm. Because hash collisions
can occur and may consume software resources, the PowerConnect may not be able to
support up to 32K MAC addresses.
•
The system can scale up to 32K MAC addresses, however, each packet processor is limited to
a maximum of 16K MAC addresses. This limit still applies, as this is a hardware limitation.
Configuring flow-based MAC address learning
To configure flow-based MAC address learning, simply enable it globally. If necessary, increase the
capacity of the MAC address table as well.
Enabling flow-based MAC address learning
To enable flow-based MAC address learning, enter the following command at the Global CONFIG
level of the CLI.
PowerConnect(config)#mac-learning-flow-based
This command enables flow-based MAC address learning. All dynamically-learned MAC addresses
are flushed from the hardware and software MAC tables and are subsequently learned using
flow-based MAC address learning.
Syntax: [no] mac-learning-flow-based
Use the no form of the command to disable flow-based MAC address learning. When disabled, all
dynamically-learned MAC addresses are flushed from the hardware and software MAC tables and
are subsequently learned using global MAC address learning.
Increasing the capacity of the MAC address table (optional)
After enabling support for flow-based MACs, you can increase the capacity of the MAC address
table of up to 32K MAC addresses. By default, up to 16K MAC addresses are supported.
NOTE
The system can scale up to 32K MAC addresses when flow-based MAC address learning is enabled.
If flow-based learning is disabled, the system cannot scale more than 16K MAC addresses.
To increase the capacity of the MAC table, enter commands such as the following.
PowerConnect(config)#system-max mac 32768
PowerConnect(config)#write memory
PowerConnect(config)#exit
PowerConnect#reload
NOTE
You must save the configuration and reload the software to place the system-max mac change into
effect.