Reference Guide

Layer 2 | 601
Restricting Layer 2 Flooding
Restricting Layer 2 Flooding is supported only on platform: e
When Layer 2 multicast traffic must be forwarded on a VLAN that has multiple ports with different speeds
on the same port-pipe, forwarding is limited to the speed of the slowest port. Restricted Layer 2 Flooding
prevents slower ports from lowering the throughput of multicast traffic on faster ports by restricting
flooding to ports with a speed equal to or above a link speed you specify.
For example, if a VLAN that has an (auto-negotiated) 100M port and a 1G port on the same port-pipe, and
you enable Restricted Layer 2 Flooding with a minimum speed of 1G, multicast traffic is only flooded on
the 1G port.
Enable Restricted Layer 2 Flooding using the command
restrict-flooding from INTERFACE VLAN mode.
In combination with
restrict-flooding, you can use the command mac-flood-list from CONFIGURATION
mode, without the
min-speed option, to allow some specific multicast traffic (identified using a MAC
address range you specify) to be flooded on all ports regardless of the
restrict-flooding configuration.
Conversely, if you want all multicast traffic to be flooded on all ports, but some specific traffic to be
restricted, use
mac-flood-list with the min-speed option, but without restrict-flooding configured. This
configuration restricts flooding only for traffic with destination multicast MAC addresses within the
multicast MAC address range you specify.
In the following example, flooding of unknown multicast traffic is restricted to 1G ports on VLAN100
using the command
restrict-flooding. However, the command mac-flood-list allows traffic with MAC
addresses 01:01:e8:00:00:00 to 01:01:e8:ff:ff:ff to be flooded on all ports regardless of link speed.
Figure 28-9. Restricting Layer 2 Multicast Flooding over Low Speed Ports
FTOS(conf)#$1:01:e8:00:00:00 ff:ff:ff:00:00:00 vlan 100-200,300
FTOS#show run | find mac-flood-list
mac-flood-list 01:01:e8:00:00:00 ff:ff:ff:00:00:00 vlan 100-200,300
[output omitted]
FTOS(conf)#interface vlan 100
FTOS(conf-if-vl-100)#restrict-flooding multicast min-speed 1000
FTOS(conf-if-vl-100)#show config
!
interface Vlan 100
restrict-flooding multicast min-speed 1000
no shutdown
FTOS(conf-if-vl-100)#