Chapter 1
| Introduction
Description of Software Features
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source IP/MAC address pairs based on static entries or entries stored in the DHCP
Snooping table.
IEEE 802.1D Bridge The switch supports IEEE 802.1D transparent bridging. The address table facilitates
data switching by learning addresses, and then filtering or forwarding traffic based
on this information. The address table supports up to 16K addresses.
Store-and-Forward
Switching
The switch copies each frame into its memory before forwarding them to another
port. This ensures that all frames are a standard Ethernet size and have been
verified for accuracy with the cyclic redundancy check (CRC). This prevents bad
frames from entering the network and wasting bandwidth.
To avoid dropping frames on congested ports, the switch provides 12 Mbits for
frame buffering. This buffer can queue packets awaiting transmission on congested
networks.
Spanning Tree
Algorithm
The switch supports these spanning tree protocols:
◆ Spanning Tree Protocol (STP, IEEE 802.1D) – This protocol provides loop
detection. When there are multiple physical paths between segments, this
protocol will choose a single path and disable all others to ensure that only one
route exists between any two stations on the network. This prevents the
creation of network loops. However, if the chosen path should fail for any
reason, an alternate path will be activated to maintain the connection.
◆ Rapid Spanning Tree Protocol (RSTP, IEEE 802.1w) – This protocol reduces the
convergence time for network topology changes to about 3 to 5 seconds,
compared to 30 seconds or more for the older IEEE 802.1D STP standard. It is
intended as a complete replacement for STP, but can still interoperate with
switches running the older standard by automatically reconfiguring ports to
STP-compliant mode if they detect STP protocol messages from attached
devices.
◆ Multiple Spanning Tree Protocol (MSTP, IEEE 802.1s) – This protocol is a direct
extension of RSTP. It can provide an independent spanning tree for different
VLANs. It simplifies network management, provides for even faster
convergence than RSTP by limiting the size of each region, and prevents VLAN
members from being segmented from the rest of the group (as sometimes
occurs with IEEE 802.1D STP).
Connectivity Fault
Management
The switch provides connectivity fault monitoring for end-to-end connections
within a designated service area by using continuity check messages which can
detect faults in maintenance points, fault verification through loop back messages,
and fault isolation with link trace messages.
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