From: OhioHondo (ohiohondo@columbus.rr.com)
Date: Tue Dec 24 2002 - 11:39:18 GMT-3
Tran Tien Phong is correct if you are using Totally Stubby Areas. If you
have to deal with Inter-Area Routes (just a stub area) I believe you have to
adjust the OSPF cost of one of the "stub to ABR" links. The minimum ospf
cost of the non-preferred link would be:
Assuming the cost of both stub to the areas ABR's are same, let's say 65 ---
Find the OSPF cost of the route between the ABR's, add that cost plus 1 to
the non-preferred between the stub and ABR.
So say the OSPF cost for the route between the ABR's is 100, the
non-preferred stub to OSPF link needs, at a minimum, to have a cost of
100+65+1.
Of course this is a minimum value. The OSPF cost of the non-preferred link
should/can be made something ridiculously high. This accommodates changes in
the network that change the OSPF cost for the path between the ABR's.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Tran Tien Phong
Sent: Tuesday, December 24, 2002 7:07 AM
To: Desmond; ccielab@groupstudy.com
Subject: RE: OSPF preferable router or path
I assume that your OSPF area is 1. Try the following:
R1:
Router ospf 100
Area 1 stub no-summary
Area 1 default-cost 20
R2:
Router ospf 100
Area 1 stub no-summary
Area 1 default-cost 10
At that time R3 will choose R2 as exit point due to lower cost.
Use "ip ospf cost" on Ethernet interfaces of R1 and R2 will not solve
the issue, because these costs will be used by the "upstream" routers of
R1 and R2 (For ex, some routers in area 0 will use these costs to choose
the best path to your ethernet network).
Hope this helps,
Tran Tien Phong
-----Original Message-----
From: Desmond [mailto:cciestudy@sympatico.ca]
Sent: Sunday, December 22, 2002 7:31 AM
To: ccielab@groupstudy.com
Subject: OSPF preferable router or path
I have following scenario. R1, R2 and R3 are on Ethernet and in an
OSPF
Totally Stub Area. Both R1 and R2 area ABRs and send default router to
R3.
R1 R2
| |
| |
-----------------
|
R3
The question is how I can make R2 is a preferable router or exit point.
Here is the solution from some Lab workbooks and scenarios.
R1
int E0
ip ospf cost 20
R2
int E0
ip ospf cost 5
I tested with my home lab. It doesn't work. I think the "ip ospf cost"
is
local significant.
Can someone provide me answer ?
Thanks in advance !
Des
.
.
.
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