6.24 OSPF Stub Areas
Before we change Area-3 into a stub,
it was a standard area.
SW2 and 4 are receiving all routes from their ABR, aka R5.
Now, we have changed this area into a stub.
R5 has also changed the contents of packets (AS External LSA)
which he sends to SW2 and 4.
R5 used to send all routes.
so many specific routes.
Once stubbed, (not stabbed)
all R5 has to send is only 0.0.0.0.
This is because
in order not to let SW2 and 4 know the detailed routes.
Thanks to this configuration,
the burden of SW2 and 4 will be extremely reduced.