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Contributor
xcieja
Posts: 18
Registered: ‎12-24-2010
0

Routing-policy between OSPF areas-how to ??

Hello,

please support me with routing plicy since i am new to that a bit...

 

On my MX80 i have 3 areas -A,B,C

Currently for OSPF routing polic says as follows:

 

policy-statement OSPF {
    term static {
        from protocol static;
        then accept;
    }
    term direct {
        from protocol direct;
        then accept;
    }


I have launched  another network (192.168.45.0) on one of my interfaces.

 

What is the simplest why to force OSPF to send updates about that network only to particular area, i.e C ??

The rest should work as it is now.

 

In other words -i would like to have in areas A,B updates about all networks except 192.168.45.0,

and in area C only updates about 192.168.45.0

 

Trusted Expert
Trusted Expert
jtb
Posts: 309
Registered: ‎08-26-2009
0

Re: Routing-policy between OSPF areas-how to ??

hi xcieja,

 

questions about filtering routing updates in link-state protocols appear from time to time (like http://forums.juniper.net/t5/Routing/ISIS-route-filtering-within-same-level/m-p/94410).

 

Again, in general, it's not possible, OSPF/IS-IS was not designed for such purpose. 

One can suggest to use some tricks or just filter LSA  type 3 on ABR (http://www.juniper.net/techpubs/en_US/junos11.2/topics/usage-guidelines/routing-applying-policies-to...) - but I had no chance to test it nor recommend it.

 

With your current OSPF policy you get LSA type 5 (External) and, AFAIK, there is no way to filter such updates. 

As with many topics: what you want to achieve ?

jtb

Distinguished Expert
aarseniev
Posts: 1,664
Registered: ‎08-21-2009
0

Re: Routing-policy between OSPF areas-how to ??

You cannot filter Type-5 LSA between regular areas, Type-5 LSA flooding scope is AS-wide, see RFC 2328 section 12.4.4

RFC 2328 also calls them "AS-external LSA".

You have to make at least 2 of your areas either stub or NSSA to be able to filter your Type-5 LSA on ABR.

You can also include your interfaces into OSPF stanza as passive and create Type-1 and Type-2 LSA, then summarize on ABR and restrict the summary using policy

http://www.juniper.net/techpubs/en_US/junos9.6/information-products/topic-collections/config-guide-r...

This trick won't work with static routes. 

HTH

Rgds

Alex 

 

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Contributor
xcieja
Posts: 18
Registered: ‎12-24-2010
0

Re: Routing-policy between OSPF areas-how to ??

[ Edited ]

1) Right now OSPF sends all the infos to all areas.

2) I have added another network -directly connected network (X)

3) I want OSPF to send updates about netowrk X only to one area i.e C - rest should work as before

 

I see it as follows:

 

policy-statement OSPF {

 

    term deny {
        from protocol direct

        from route-filter X/24 exact;

        to area A,B
        then reject;

 

term accept {
        from protocol direct

        from route-filter X/24 exact;

        to area C
        then accept;


    term static {
        from protocol static;
        then accept;
    }
    term direct {
        from protocol direct;
        then accept;
    }

 

 

Please correct ,me if i am wrong

Distinguished Expert
aarseniev
Posts: 1,664
Registered: ‎08-21-2009
0

Re: Routing-policy between OSPF areas-how to ??

You are creating Type-5 LSAs with your policy named "OSPF".

And this policy won't restrict Type-5 LSA flooiding for the reasons I outlined in my previous post.

HTH

Alex

 

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Contributor
xcieja
Posts: 18
Registered: ‎12-24-2010
0

Re: Routing-policy between OSPF areas-how to ??

[ Edited ]

Thank you -i will have to do it other way.

 

Ok -but strange for me is that LSA 5 is AS-wide case but -but filtering is implementation case....RFC has nothing to do that..

 

In other words- are somwere docs saying that i can not filter LSA-5 and explianed why???

 

As far as i remember LSA are updates are packets -so we should be able to play with IP adresses as with other packets ...

 

Why here not ???

 

Regards

Trusted Contributor
Saurabh
Posts: 171
Registered: ‎09-08-2009
0

Re: Routing-policy between OSPF areas-how to ??

As per RFC an OSPF speaking router should share complete database with its neighbor within area. I.e.. LSDB should be identical.. This is wat we call as OSPF rule.

 

If you try to filter out some LSAs (say LSA 5) learned via your OSPF neighbor from area X to be advertised to area Y its actually breaching the rule.

 

In short you can control your own( i.e.. Router's it self) advertisements  in to OSPF domain not the learned LSAs.

 

Definitely We have some options like stub,nssa like our one of the friend has already explained.

 

Hope this helps.

Saurabh Joshi
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