Spanning Tree Protocol Support - Proxim RangeLAN2 7500 User Manual

Spanning Tree Protocol Support

RangeLAN2 7500 meets the IEEE 802.1d Spanning Tree Proto-
col specification. This protocol was designed to handle cases in
a complex bridged network (multiple bridges) where loops are
created either unintentionally or to provide redundancy in the
network. The bridges will configure themselves into a spanning
tree topology removing any loops within the network. If you are
administering a network with more than one bridge
(RangeLAN2 or otherwise), you will probably need to have
some understanding of this protocol so that you can configure
your bridges for optimum performance.
One of the bridges will become the root of the spanning tree.
This root is determined by the bridge with the lowest spanning
tree priority on the network. This bridge determines when all the
bridges will broadcast their priorities, physical addresses, activity
states, etc. This communication is sent in what are called hello
packets, and the root bridge determines the interval between
these packets called the hello time.
Once a root to the tree has been established, all other bridges on
the network must become the branches. The order of the
branches is determined by the spanning tree priority, path cost
(number of jumps away from the root), and port priority for
each bridge and each port on each bridge.
In the case where there are redundant bridges causing loops in
the network, these loops are resolved by one of the bridges
becoming inactive. This means the bridge will no longer for-
ward packets of data that are sent to it. If the loops were not
resolved, the same packet of data might travel around the net-
work ad infinitum.
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