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OSPF Problem

Hi All,

I have a customer which has the following setup.

R1

/ \

R2 R3

\ /

R4

R1 is at the central site and has the data center hosted. The link between R1 and R2, R2 and R4 are in Area0. The links between R1 and R3, R3 and R4 are in Area1.

Users at R4 wants to access some SAP servers which are hosted at R1. The link between R4 and R2 is a slow speed link and the link between R4 and R3 is a 2 MBPS LL.

The problem is that the R4 is learing the routes to the SAP servers segment Via R2 with slow speed links (a backup link) and hence users are facing a problem to access the SAP application.

We have tried changing the cost on the R2 and R4 interfaces from default 48 to 1000 and more but still it learns the route Via R2. When we shut the interface down at R4, the router learns the route via R3 (which it should be and what we want) everything works fine.

Let me know your thoughts on this and how can we fine tune that.

Regards,

-amit singh

5 REPLIES

Re: OSPF Problem

Hello Amit,

Changing the cost to a higher value on the interface in R1 that connects to R2 should do the job.

Also, are you setting the correct bandwidth on the interfaces? that is advisable too, these should do its job too, as cost is 10^8/int bandwidth (by default)

give us a sample of the metrics on R4 for routes in R2, for both cases (with and without R3).

HTH,

if it does, please rate this post.

Vlad.

Re: OSPF Problem

Hi Amit,

Can you also confirm if the lan of R1 and the lan of R4 are in which area?

Regards,

Ankur

Re: OSPF Problem

Hi Amit,

If the LAN interfaces on R1 and R4 are in area0 it will be preferred as intra area routes are prefererd over inter area routes no matter whatever the total cost of the route is learned from different interfaces.

Regards,

Ankur

Re: OSPF Problem

Hello,

OSPF will always - independant of metric - prefer INTRA area routes over INTER area routes.

The way you described the setup I would assume, that R4 has the network of the SAP servers learned through LSA type 1 in area 0 and through LSA type 3 in area 1.

If this is the case then there is little to do, other than setting up a virtual link through area 1 between R1 and R4 or converting everything to area 0.

I would recommend to look for a solution without virtual links.

Hope this helps! Please rate all posts.

Regards, Martin

New Member

Re: OSPF Problem

Hi Amit,

Weight will do the job properly. R1 is advertising the routes to servers then r4 will receive routes from routers R2 and R3. So give the R4 to R3 route higher weight to reach the server farm..

Regards

Mahi

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