From: Scott Morris (swm@emanon.com)
Date: Thu Nov 04 2004 - 00:18:58 GMT-3
You're looking at two different pieces of the puzzle.
Remember that things get processed within the OSPF RIB first, so concepts of
metrics will come into play regarding a preferred unique route.
If OSPF has an identical route learned within an area (Type 1 or Type 2 LSA)
then those are preferred first. Then a Type 3 LSA comes next (inter area).
Then a Type 5 LSA (external). That is BEFORE cost is looked at.
So think about the LSA's being in numerical order of preference. All of
these will have an AD of 110. So AFTER OSPF has made its selection of
individual unique routes within the RIB, they are handed to the routing
table.
ONLY at the routing table part is where the AD comes into play. The routing
table could honestly care less about intra, inter or external origin!
HTH,
Scott Morris, MCSE, CCDP, CCIE4 (R&S/ISP-Dial/Security/Service Provider)
#4713, JNCIP, CCNA-WAN Switching, CCSP, Cable Communications Specialist, IP
Telephony Support Specialist, IP Telephony Design Specialist, CISSP
CCSI #21903
swm@emanon.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Edwards, Andrew M
Sent: Wednesday, November 03, 2004 6:34 PM
To: ccielab@groupstudy.com
Subject: Re: OSPF inter vs intra area routes
All,
I'm looking in the archive and I cant seem to get a clear picture on this...
its my understanding that by default all ospf routes have an AD of 110.
But, I've heard rumor that OSPF prefers intra over inter area routes. I
think Jeff Doyle vol 1 sort of supports that idea too with the SPF being run
on intra area routes and all inter areas get built via distance vector
methodology (unless I am completely misinterpreting).
Does this occur by default or is this something we have to explicitly
configure under OSPF distance command?
andy
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