ZyXEL Communications XGS4700 Series, Manual

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XGS4700-48F User’s Guide
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H A P T E R
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Error Disable
This chapter shows you how to configure the rate limit for control packets on a
port, and set the Switch to take an action (such as to shut down a port or stop
sending packets) on a port when the Switch detects a pre-configured error. It also
shows you how to configure the Switch to automatically undo the action after the
error is gone.
32.1 CPU Protection Overview
Switches exchange protocol control packets in a network to get the latest
networking information. If a switch receives large numbers of control packets,
such as ARP, BPDU or IGMP packets, which are to be processed by the CPU, the
CPU may become overloaded and be unable to handle regular tasks properly.
The CPU protection feature allows you to limit the rate of ARP, BPDU and IGMP
packets to be delivered to the CPU on a port. This enhances the CPU efficiency and
protects against potential DoS attacks or errors from other network(s). You then
can choose to drop control packets that exceed the specified rate limit or disable a
port on which the packets are received.
32.2 Error-Disable Recovery Overview
Some features, such as loop guard or CPU protection, allow the Switch to shut
down a port or discard specific packets on a port when an error is detected on the
port. For example, if the Switch detects that packets sent out the port(s) loop
back to the Switch, the Switch can shut down the port(s) automatically. After that,
you need to enable the port(s) or allow the packets on a port manually via the
web configurator or the commands. With error-disable recovery, you can set the
disabled port(s) to become active or start receiving the packets again after the
time interval you specify.