3Com CoreBuilder 9000, Руководство пользователя

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346 C
HAPTER
12: E-IISP P
ROTOCOL
Alternate routes are desirable for the following reasons:
Dividing the load between nodes over several links reduces congestion
(see next section)
If one link fails, an alternate link can be used.
If the node cannot be found or accessed via a link, it can be searched
through another link after
crankback.
Rules for Creating Alternate Routes
The following rules apply when you plan alternate routes:
To have a general overview of the entire network, carefully draw all
the network nodes and their connections .
When you create alternate routes within the same tree, connect to an
ancestor, not to another branch.
Keep the E-IISP routing algorithm in mind as described in “E-IISP
Hierarchic Routing Algorithm”.
Eliminate infinite loops by configuring the Hop Count Limit to be one
more than the number of hops in the longest path through the graph.
(The Hop Count Limit is 7 for most hierarchial networks.)
Consider all possible ups and downs through the trees with each
alternate route.
Create alternate routes with “equal” matches so that the calls are
distributed.
Routing Table
As the routing algorithm establishes the internal connections, it also
establishes a routing table. For each connection it establishes, the
algorithm stores alternate links that it might have used instead of the one
it did use. This table can be used either for load balancing (see next
section) or for establishing an alternate connection after crankback.