Radware Alteon, Инструкция по применению

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Alteon Application Switch Operating System Application Guide
Spanning Tree Protocol
100
Document ID: RDWR-ALOS-V2900_AG1302
The generic action of an Alteon on receiving a BPDU is to compare the received BPDU to its own
BPDU that it transmits. If the received BPDU is better than its own BPDU, it will replace its BPDU
with the received BPDU. Then, Alteon adds its own bridge ID number and increments the path cost
of the BPDU. Alteon uses this information to block any necessary ports.
Determining the Path for Forwarding BPDUs
When determining which port to use for forwarding and which port to block, Alteon uses information
in the BPDU, including each bridge priority ID. A technique based on the "lowest root cost" is then
computed to determine the most efficient path for forwarding.
For more information on bridge priority, port priority, and port cost, refer to the Alteon Application
Switch Operating System Command Reference. Much like least-cost routing, root cost assigns lower
values to high-bandwidth ports, such as Gigabit Ethernet, to encourage their use. For example, a 10
Mbps link has a “cost” of 100, a 100 Mbps (Fast Ethernet) link carries a cost of 10, and a 1000 Mbps
(or Gigabit Ethernet) link has a cost of 1. The objective is to use the fastest links so that the route
with the lowest cost is chosen.
Bridge Priority
The bridge priority parameter controls which bridge on the network is the STP root bridge. To make
one Alteon the root bridge, configure the bridge priority lower than all other switches and bridges on
your network. The lower the value, the higher the bridge priority. The bridge priority is configured
using the
/cfg/l2/stg/brg/prior
command.
Port Priority
The port priority helps determine which bridge port becomes the designated port. In a network
topology that has multiple bridge ports connected to a single segment, the port with the lowest port
priority becomes the designated port for the segment. The port priority is configured using the
/cfg/l2/stg/port/prior
command.
Port Path Cost
The port path cost assigns lower values to high-bandwidth ports, such as Gigabit Ethernet, to
encourage their use. The cost of a port also depends on whether the port operates at full-duplex
(lower cost) or half-duplex (higher cost). For example, if a 100 Mbps (Fast Ethernet) link has a
"cost" of 10 in half-duplex mode, it will have a cost of 5 in full-duplex mode. The objective is to use
the fastest links so that the route with the lowest cost is chosen. A value of 0 indicates that the
default cost will be computed for an auto-negotiated link speed.
Spanning Tree Group Configuration Guidelines
This section provides guidelines for configuring STGs, including:
• Adding a VLAN to a Spanning Tree Group, page 101
• Creating a VLAN, page 101
• Rules for VLAN-Tagged Ports, page 101
• Adding and Removing Ports to and from STGs, page 101
• Spanning Tree Implementations in Trunk Groups, page 102