From: ccie2be (ccie2be@nyc.rr.com)
Date: Sat Jan 15 2005 - 12:26:07 GMT-3
Thanks Brain and what the heck are you doing up at 6:30 in the morning on a
Saturday?
Anyway...
After spending hours trying to use the distance command to make one path
preferred
over another, I was starting to get the feeling this wasn't possible because
of what you just said.
BTW, this question was inspired by your lab 15.
I was trying to figure out all the ways I could make the ibgp peering
between
the loopbacks of R4 and R5 prefer the path via R3.
But, based on what you just said, it looks like changing the AD's for these
loopback
addresses on R4 and R3 won't accomplish this. Because no matter what, R5
will
always prefer the intra-area path to R4's loopback regardless of path metric
via R3
Do you agree?
One other possible way I though of to accomplish this is to create a tunnel
between
R3 and R4 over the eigrp link. And, then run ospf over that tunnel and make
the ospf cost of the path
R5 -> R3 -> R4 lower than the ospf cost of the isdn link between R4 and R5.
I haven't tried this yet, but I can't see any reason why this wouldn't work.
This should work, don't you think?
Aside from a tunnel between R3 and R4, assuming this can work, is there any
other way to
make R5 and R4 prefer the path via R3?
BTW, this lab 15 is a great lab. I've learned so much from working on this
lab, I can't even tell
you.
Thanks, Tim
----- Original Message -----
From: "Brian Dennis" <bdennis@internetworkexpert.com>
To: "ccie2be" <ccie2be@nyc.rr.com>; "Group Study" <ccielab@groupstudy.com>
Sent: Saturday, January 15, 2005 9:28 AM
Subject: RE: ospf path selection: Internal vs External
The order of preference regardless of cost is:
Intra-area over Inter-area
Inter-area over External Type-1
External Type-1 over External Type-2
The only time that this order of preference is not taken into
consideration is when the router is comparing OSPF routes from different
OSPF processes.
For information regarding OSPF route selection, you can look over RFC
2328 OSPF Version 2 - Section 16 (Calculation of the routing table)
http://www.internetworkexpert.com/rfc/rfc2328.txt
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: Saturday, January 15, 2005 3:13 AM
To: Group Study
Subject: ospf path selection: Internal vs External
Hi guys,
I hope this isn't a completely dumb question, but...
If an ospf router has a choice between 2 paths to a subnet where 1 path
is
via
an External route and the other path is via an ospf internal (inter-area
or
intra-area)
route, is that taken into consideration in determining which path is
installed in the
route table?
If that is considered, does ospf automatically prefer one route over the
other
or does the spf
calculation ignore that?
( For this to occur, I realize that an ospf route has to be
redistributed out
of ospf and then back in,
but in the scenario I'm working on, that's just what I want to do and I
want
ospf to choose the external route
over the internal route.)
Thanks in advance, Tim
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