Unknown Unicast Flooding On Vlan Ports; Flow Based Mac Learning - Dell PowerConnect B-RX Configuration Manual

11
Other VLAN features

Unknown unicast flooding on VLAN ports

Unknown unicast packets do not have a specific (or unicast) recipient. In order for these "special"
packets to reach their intended recipient, they needed to be sent on all ports of the VLAN (or
"flooded" across the VLAN).
By default, the device performs hardware flooding for unknown unicast packets. However, if uplink
VLANs or protocol-based VLANs are configured, this default behavior is overridden and software
flooding is enabled.
To disable unicast hardware flooding on a VLAN ports and enable software flooding, enter
commands such as the following.
BigIron RX(config)# vlan 2
BigIron RX(config-vlan-2)# no unknown-unicast-flooding
BigIron RX(config-vlan-2)# exit
BigIron RX(config)# reload
Syntax: [no] unknown-unicast-flooding

Flow based MAC learning

In this release, the cpu-flooding command that disables hardware flooding of unknown unicast,
multicast, and broadcast packets on all VLAN has been added. When using this command,
unknown unicast packets will go to the CPU and will be CPU forwarded. Source MAC learning will be
done by CPU. The first packet for unknown DA will go to the CPU and CPU will program the hardware
on demand. Any supplemental packets will be forwarded by the hardware.This will allow MAC
learning only where necessary and at a system level to allow more than 16k MACs. In addition, a
MAC will be learned only on the port or packet processor it was received.
Enabling CPU flooding
To enable CPU based flooding of unknown unicast, broadcast and multicast packets, enter the
following command at the global configuration level.
BigIron RX(config)# cpu-flooding
To enable flow based MAC learning and CPU flooding for unknown unicast packets only, enter the
following command at the global configuration level.
BigIron RX(config)# cpu-flooding unknown-unicast
To enable CPU based flooding for broadcast and multicast packets, enter the following command at
the global configuration level.
BigIron RX(config)# cpu-flooding multicast
Syntax: [no] cpu-flooding [multicast] [unknown-unicast]
Use the multicast parameter to specify CPU flooding for broadcast and multicast packets.
320
•
You cannot enable this feature on the designated management VLAN for the device.
•
If you enable this feature on a VLAN that includes a trunk group, hardware flooding for
Layer 2 multicast and broadcast packets occurs only on the trunk group's primary
port. Multicast and broadcast traffic for the other ports in the trunk group is handled
by software.
BigIron RX Series Configuration Guide
53-1002253-01