LevelOne GEL-1061 User Manual page 32

Chapter 1
| Introduction
Description of Software Features
Static MAC Addresses
IP Address Filtering
IEEE 802.1D Bridge
Store-and-Forward
Switching
Spanning Tree
Algorithm
A static address can be assigned to a specific interface on this switch. Static
addresses are bound to the assigned interface and will not be moved. When a static
address is seen on another interface, the address will be ignored and will not be
written to the address table. Static addresses can be used to provide network
security by restricting access for a known host to a specific port.
Access to insecure ports can be controlled using DHCP Snooping which filters
ingress traffic based on static IP addresses and addresses stored in the DHCP
Snooping table. Traffic can also be restricted to specific source IP addresses or
source IP/MAC address pairs based on static entries or entries stored in the DHCP
Snooping table.
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.
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.
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
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