problem with ospf spf

Unanswered Question
Jan 17th, 2008

We are having abr. It is calcualating SPF after 2 minutes which makes the area unstable and lot of problems. Any remedies for that.

I have this problem too.
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s.arunkumar Thu, 01/17/2008 - 22:48

Do u mean to say it calculates every two min?

Normaly an spf calculation is triggerd when a change in the topology occurs.Do check for any link state changes or flapping happening in the connected areas of the ABR..

check for the reason using "show ip ospf statistics"

a good discussion regarding the same is here.

arun :)

shivlu jain Thu, 01/17/2008 - 23:41

hi areun thanks the post helped me lot and i am facing the same problem as it was mentioned.



shivlu jain Thu, 01/17/2008 - 23:50

arun dows it makes sense if we mark that area as stub area.

My most of the backhaul links are over radio frequency.



shivlu jain Fri, 01/18/2008 - 00:01

arun if we are3 having two interfaces and onw is primary and another is secondry means we are playing with cost , if primary is not getting but secondary is getting down then does secondary can affect the spf calculations.



s.arunkumar Fri, 01/18/2008 - 00:32

Any link state changes generates lsa reflecting the changes,and that will trigger an spf calculation.Now adjusting the cost and selecting a link as primary is only for reflecting in the routing table(and hence for packet forwarding),ur ospf database still will have lsa for the secondary link.Hence,the secondary link getting down also can cause spf calcluation .

I didnt got what u mean by "making stub " in one of the above post..


shivlu jain Fri, 01/18/2008 - 01:35

I got ur point.

Now come to the stub part:- Actually my area 0 is not stable just becasue of this my all areas are affected. I have an area let say 10 it is connected to area 0.Now everytime the area0 links got disturbed my area 10 is also hampered.Thats why i want to make area 10 as stub.

Why i want this because i am having one 2811 in area 10 and its process goes 100% after 2 minuutes and after 2 minutes the spf does its calculations.



s.arunkumar Fri, 01/18/2008 - 01:54

Now let me tell u,a state change in one area will not cause an spf to be run on another area.,ie,a state change of any link in area 0 will cause spf to run on area 10 routers. Type 3 lsa will not trigger an spf,but a partial spf do run,but i doubt a partial spf will cause ur process to utilize these much,because partial spf is just removing a interarea route from routing table.

Please a have look on a link a given to u on above post having a good discussion about partial spf..

Is ur router an ABR??then the spf running is because of the link changes in its connected area 0 itself.Making another area stub may not help here.



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