Dell 28XX Switch User Manual


 
Dell PowerConnect 28xx Systems User Guide 11
Summary of PowerConnect Models
The following table summarizes the PowerConnect models.
Features
General Features
Management Modes
The device supports the following modes:
Managed Mode
— Provides switch management through the web interface.
Unmanaged Mode
— In this mode, the device operates as a hub with default configuration, and
configuration cannot be changed.
Secure Mode
— This mode keeps the existing configuration active, but it prevents users from making
configuration changes by removing the IP address of the device so that it becomes inaccessible for
configuration.
For more information about the management modes, see "Management Modes" on page 49.
Head of Line Blocking Prevention
Head of Line (HOL) blocking results in traffic delays and frame loss caused by traffic competing for the
same egress port resources. HOL blocking queues packets, and the packets at the head of the queue are
forwarded before packets at the end of the queue. By default, the device is configured so that the HOL
blocking prevention mechanism is active at all times, except when QoS (Quality of Service), Flow
Control or Back Pressure is active on a port where the HOL blocking prevention mechanism is disabled
on the whole system.
Back Pressure Support
On half-duplex links, the receiving port prevents buffer overflows by occupying the link so that it is
unavailable for additional incoming traffic. The user may enable or disable this feature on a
per-port basis. The default status on all ports is set to OFF.
Table 1-1. PowerConnect Models
Model Copper Ports/
RJ-45 Connectors
Optical Ports/
GbE
RS232 serial port -
baud rate is 9600 bps
Fans
PowerConnect 2808 8 built-in 10/100/1000 Base-T ports none Internal console port none
PowerConnect 2816 16 built-in 10/100/1000 Base-T ports none External console port none
PowerConnect 2824 24 built-in 10/100/1000 Base-T ports 2 SFP (combo) External console port 1
PowerConnect 2848 48 built-in 10/100/1000 Base-T ports 4 SFP (combo) External console port 32