Operation
10
Backup Operation
The AT-3675 bridge software allows you to establish redundant
interconnections between the same two networks. This feature provides
backup should the bridge or its network connection fail. The primary bridge
and its backup communicate with each other in accordance with the SNMP-
standard STP protocol. Because of this signal, the Activity indicators will
blink every few seconds, even if there is no other network activity. The STP
algorithm can be disabled using a network management package such as
SunNet™ Manager or SNMPc.
Application Guidelines
In planning the placement of bridges, network topology, network length, node
count and natural cluster boundaries are all factors you must take into
consideration for the best performance.
Network Topology
A network with bridged sub-networks takes on one of two basic forms. The
first is a cascaded network, where a set of sub-networks are connected
together by a series of bridges. An example of this configuration is given in
Figure 4. A cascaded-bridged network is useful when the number of bridges
is small. If many bridges are used, the delay associated with each bridge may
accumulate to unacceptable levels between networks at the extremities.
The second form used is a tree topology. The simplest configuration of a tree
topology is one level deep and is known as a backbone network. Figure 5
shows this type of tree topology. In a backbone configuration, each workgroup
has its own network, and there is one network used only for communicating
between the workgroups. The advantages of a tree network topology are
listed below:
❑
There are never more than two bridges between any two
sub-networks. The delays introduced by bridges are therefore
minimized.
❑
As long as the backbone network is operating correctly, any fault
within a sub-network has no effect on other sub-networks.
❑
Faults are isolated to a single sub-network and are therefore easier to
find.
Figure 4: A Cascaded Bridged
Network
Sub-network A
Sub-network B
Sub-network C
Sub-network D
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CentreCOM
3675
CentreCOM
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CentreCOM
