22 C
HAPTER
1: S
UPER
S
TACK
II S
WITCH
M
ANAGEMENT
S
OFTWARE
Units in the Switch 1100/610 family support three forwarding modes in
addition to Store and Forward:
■
Fast Forward
— Packets are forwarded as soon as the destination
address is received and processed. With Fast Forward, packets take
less time to be forwarded, but all error packets are propagated onto
the network because no time is allowed for checking.
■
Fragment Free
— Packets are forwarded when at least 512 bits of the
packet is received, which ensures that collision fragments are not
propagated through the network. With Fragment Free, packets take
less time to be forwarded, but all error packets except fragments are
propagated.
■
Intelligent
— The Switch monitors the amount of error traffic on the
network and changes the forwarding mode accordingly. If the Switch
detects less than 20 errors a second, the forwarding mode is set to
Fast Forward. If the Switch detects 20 or more errors a second, the
forwarding mode is set to Store and Forward until the number of
errors a second returns to zero.
For information about setting the forwarding mode for units in the
Switch 1100/610 family, see
“Configuring the Advanced Stack Settings”
on
page 76
.
Duplex Modes
All the ports on your Switch can be set to one of two duplex modes:
■
Half duplex
— Allows packets to be transmitted and received, but not
simultaneously. This is the default Ethernet duplex mode.
■
Full duplex
— Allows packets to be transmitted and received
simultaneously and, in effect, doubles the potential throughput of a
link. In addition, full duplex supports 100BASE-FX cable runs of up to
2km (6562ft).
To communicate effectively, both ends of a link must use the same duplex
mode. If the link uses an auto-negotiating connection, this is done
automatically. If the link uses a connection that is not auto-negotiating,
both ends must be set to half duplex or full duplex manually.
For more information about setting the duplex mode of a port, see
“Configuring a Port”
on
page 59
.
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