User guide

Physical and Layer 2 Interfaces 47
Software Release 2.4.1
C613-02021-00 REV B
able to determine the duplex mode of the link and must be forced to use the
correct mode. Switch ports autonegotiate by default when they are connected
to a new device.
To force ports to use a fixed speed and duplex mode, enter the command:
SET SWITCH PORT={port-list|ALL}
SPEED={AUTONEGOTIATE|10MHALF|10MFULL|100MHALF|100MFULL}
Limiting Switch Traffic
You can make some choices about how switch ports respond when there is
more traffic than the network or the switch ports can handle easily. Any choices
you make affect all switch ports on the base router unit.
The default settings for commands that limit traffic are adequate for most
situations.
By default, back pressure for flow control for half duplex ports is turned on:
SET SWITCH BACKPRESSURE=ON
By default, flow control using pause frames for full duplex ports is turned on:
SET SWITCH FLOWCONTROL=ON
Once the system resource becomes available the switch transmission by the
link partner of the port can resume.
You can set the global retransmission time delay for all switch ports operating
in half duplex mode. When the port attempts to transmit a packet and
encounters a collision, the switch stops transmission and starts a short delay
(backoff) before attempting re-transmission. If AGGRESSIVE is specified, the
time delay is shorter. If NORMAL is specified, the time delay is standard. The
default is NORMAL.
SET SWITCH BACKOFF={AGGESSIVE|NORMAL}
By default, switch ports will repeat attempts to transmit a packet until they
succeed:
SET SWITCH EXCESSIVECOLLISION=RETRY
Packet buffers available in the buffer pool are shared by all switch ports. By
default, these are allocated automatically according to the amount of traffic at
each port (ADAPTIVE). To limit the number of buffers available for any port,
enter the command:
SET SWITCH BUFFERPOOL={EQUAL|ADAPTIVE}
By default, broadcast and multicast packets are discarded if they are in excess
of 25% the line rate:
SET SWITCH BROADCASTLIMIT=ON
Table 8: Autonegotiation preferences for switch ports.
Preference 10/100 Ethernet switch ports
Highest
100 Mbps, Full duplex
100 Mbps, Half duplex
10Mbps, Full duplex
Lowest
10Mbps, Half duplex