DELL S50V User Manual

Broadcast Storm Control | 1043

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This chapter contains the following configuration topics:

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FTOS Storm Control is a preventative measure against unexpectedly high rates of broadcast or multicast 
packets; these traffic bursts are called storms. If the rate of these packets on ingress or egress exceeds a 
user-defined threshold, FTOS, when configured, can suppress forwarding for these packets until the packet 
rate falls back to the configured limit.

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Layer 2 Broadcasts—A switch might not have an entry in its MAC address table that matches a 
packet’s destination MAC. In this case, the switch floods the packet on the VLAN. These packets are 
called unknown-packets; they cause unnecessary extra traffic and can reduce network performance.

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Layer 3 Broadcast Packets—There are two types of Layer 3 broadcast packets: the all-hosts 
broadcast, the IP address of which is 255.255.255.255, and the subnet broadcast address, the address of 
which has the host portion of the address set to all ones; for example, 10.11.1.255/24 is the broadcast 
address for the 10.11.1.0 network. Some protocols utilize broadcasts more than others and so storm 
control might be useful to prevent congestion.

Multicast Packets—Multicast packets are packets that use a special range of MAC and IP addresses 
to send packets to a group of hosts, rather than a single host. Some multicast applications can cause 
excessive bandwidth consumption, and storm control can be used (in conjunction with IGMP 
Snooping) to limit multicast traffic.