Modular L3 Ethernet Switch User’s Guide
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Figure 5- 3: Network LAN Connectivity
Broadcast Storms
Broadcast storms are a common problem on today’s networks. Basically, they consist of
broadcast packets that flood and/or are looped on a network causing noticeable performance
degradation and, in extreme cases, network failure. Broadcast storms can be caused by network
loops, malfunctioning NICs, bad cable connections, and applications or protocols that generate
broadcast traffic, among others.
In effect, broadcast storms can originate from any number of sources, and once they are started,
they can be self-perpetuating, and can even multiply the number of broadcast packets on the
network over time. In the best case, network utilization will be high and bandwidth limited until
the hop counts for all broadcast packets have expired, whereupon the packets will be discarded
and the network will return to normal. In the worst case, they will multiply, eventually using up
all the network bandwidth (although network applications will usually crash long before this
happens), and cause a network meltdown.
Broadcast storms have long been a concern for network administrators with routers traditionally
being used to prevent their occurrence, and if that failed, to at least limit their scope. However,
with the advent of VLANs, switches are now able to limit broadcast domains better and cheaper
than routers. Also, many switches, including the DES-6300 series, have broadcast sensors and
filters built into each port to further control broadcast storms.
Segmenting Broadcast Domains
VLANs can be used to segment broadcast domains. They do this by forwarding packets only to
ports in the same VLAN. Thus, broadcast packets will only be forwarded to ports that are
members of the same VLAN. Other parts of the network are effectively shielded. As a result, the
Summary of Contents for DES-6300
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