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9033630 Product Overview 7
Feature Summaries
The following summaries describe VH-4802 features in areas such as
standards compliance, functionality, performance, and options.
IEEE 802.1D Bridge
The VH-4802 switch is fully compliant with IEEE 802.1D transparent
bridging specifications. An address table is provided for learning, filtering,
and forwarding. The switch can support up to a maximum of 12K
addresses. Addresses are automatically learned by the switch, and can
be individually assigned specific forwarding treatment by the network
administrator if desired. Forwarding table configuration can be made out-
of-band via the console interface or in-band via SNMP or Telnet. Static
and dynamic addresses are both stored in this table. One static address
is assigned per port by default. The Static Unicast Address Table
Configuration screen in the console menus allows you to assign additional
static addresses if required.
Spanning Tree Protocol
The VH-4802 switch supports the IEEE 802.1D Spanning Tree Protocol.
This protocol allows redundant connections to be created between
different LAN segments for purposes of fault tolerance. Two or more
physical paths between different segments can be created through the
switch, with the Spanning Tree Protocol choosing a single path at any
given time and disabling all others. If the chosen path fails for any reason,
a disabled alternative is activated, thereby maintaining the connection.
This prevents network traffic from circulating in an endless loop formed by
multiple connections to the same LAN segment.
Spanning Tree parameters are configurable using the Spanning Tree
Configuration Menu of the console menus, the on-board Web agent, or
via SNMP (see Appendix B, “Spanning Tree Concepts,” in the
Management Guide for more information).
Frame Buffering and Frame Latency
The VH-4802 switch is a store-and-forward switching device. Each frame
is copied into switch memory before being forwarded to another port. This
method ensures that all forwarded frames conform to a standard Ethernet
frame size and have a correct cyclic redundancy check (CRC) for data
integrity. This switching method prevents bad frames from traversing the
network and using up valuable network bandwidth, as with cut-through
switching technology.
To minimize the possibility of dropping frames on congested ports, the
VH-4802 switch provides 512 KB of frame buffering per port. This buffer
space is used to queue packets for transmission on congested networks.
This is an additional advantage over cut-through switching technology,
which drops packets immediately when experiencing collisions.
ELS100-48tx2m.book Page 7 Thursday, November 16, 2000 4:59 PM