A technique I like to use in hub-and-spoke networks is to declare a
LAN interface as area 0.0.0.0. If I subsequently add a backup
router, I'll also connect that to the same LAN. It's reasonable to
connect TFTP, DHCP, etc., there as well, but not any application
servers.
If I do have application servers, I'll hang another LAN interface off
the core router and declare them in their own area. Just considering
backup, there's probably going to be server-to-server communications
that doesn't belong in the backbone.
But to answer the general question, yes, dynamically routed
inter-area routing in OSPF must go through area 0.0.0.0. There are
some proposals for alternatives in the IETF, but I'd say they are
mostly at the talking stage.
When I need to break OSPF hierarchy, it's most often for traffic
engineering, and I'll set it up with a static route explicitly NOT
redistributed into OSPF, and with an administrative distance lower
than OSPF. I can always have OSPF through-the-backbone routing as a
backup.
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=9445&t=9268
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