C
HAPTER
9
| Congestion Control
Storm Control
– 232 –
You can protect your network from traffic storms by setting a threshold for
broadcast, multicast or unknown unicast traffic. Any packets exceeding the
specified threshold will then be dropped.
CLI REFERENCES
◆ "switchport packet-rate" on page 755
COMMAND USAGE
◆ Storm Control is disabled by default.
◆ Broadcast control does not effect IP multicast traffic.
◆ When traffic exceeds the threshold specified for broadcast and
multicast or unknown unicast traffic, packets exceeding the threshold
are dropped until the rate falls back down beneath the threshold.
◆ Storm control is a hardware level function. Traffic storms can also be
controlled at the software level using automatic storm control which
triggers various control responses (see "Automatic Traffic Control" on
page 234). However, only one of these control types can be applied to a
port. Enabling hardware-level storm control on a port will disable
automatic storm control on that port.
◆ Rate limits set by the storm control function are also used by automatic
storm control when the control response is set to rate limiting.
◆ Using both rate limiting and storm control on the same interface may
lead to unexpected results. For example, suppose broadcast storm
control is set to 5000 kbps by the command “switchport broadcast
packet-rate 5000,” and
the rate limit is set to 200000 kbps by the
command “rate-limit input 200000"
on a Gigabit Ethernet port. Since
200000 kbps is 1/5 of line speed (1000 Mbps), the received rate will
actually be 1000 kbps, or 1/5 of the 5000 kbps limit set by the storm
control command. It is therefore not advisable to use both of these
commands on the same interface.
◆ The description of effective rate limiting (see Command Usage under
"Rate Limiting" on page 229) also applies to storm control.
N
OTE
:
Due to a chip limitation, the switch supports only one limit for both
ingress rate limiting and storm control (including broadcast unknown
unicast, multicast, and broadcast storms).
PARAMETERS
These parameters are displayed in the web interface:
◆ Interface – Displays a list of ports or trunks.
◆ Type – Indicates interface type. (1000Base-T or SFP)
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