OSPF在处理Summary-LSAs的时候,是存在水平分割现象的。
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Summary-LSAs
To determine which routes to advertise into an attached Area
A, each routing table entry is processed as follows.
Remember that each routing table entry describes a set of
equal-cost best paths to a particular destination:
o Only Destination Types of network and AS boundary router
are advertised in summary-LSAs. If the routing table
entry's Destination Type is area border router, examine
the next routing table entry.
o AS external routes are never advertised in summary-LSAs.
If the routing table entry has Path-type of type 1
external or type 2 external, examine the next routing
table entry.
o Else, if the area associated with this set of paths is
the Area A itself, do not generate a summary-LSA for the
route.[17]
o Else, if the next hops associated with this set of paths
belong to Area A itself, do not generate a summary-LSA
for the route.[18] This is the logical equivalent of a
Distance Vector protocol's split horizon logic.
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