OSPF, MPLS and ISDN

[katerina.dardoufa]

Dear community,

I have the following issue which I cannot solve.

My company is  migrating to GETVPN and we use OSPF to connect to our provider. On its  PEs the provider has set max-lsa to 3000, where 3000 is the sum of all  LSAs of my company's routers connected to that specific PE. For  super-extra redundancy we want to still use our previous backup  connection, so when either the main line, or the ADSL line fail (these  are not on our router, but on the CPE), traffic can be routed through  the backup-ISDN. We are also using OSPF in our internal network, and the  IP address of the ISDN-backup and that of the connection to the  provider (CPE) belong to the same ospf area.

When the ip address  of the BRI is participating in OSPF,  LSAs advertised to the PE are  about 2000 for every remote site, so on the PE the max-lsa number is  very quickly reached, resulting in loss of connectivity!!! For the time  being ISDN is not participating in OSPF so as to overcome the above  issue.

I was wondering if you can think of a way to add  the ISDN in the routing process, when connectivity through the main and  DSL link fail, but without sending the LSAs sent through the BRI to the  provider.

Thanks in advance

Katerina

[Mathias Garcia]

ip ospf demand-circuit
This interface level command disables the periodic LSA flooding and hellos.

Check the link for a complete guide.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a8f.shtml#lsarefresh

[katerina.dardoufa]

Thank you for this very interesting link. I am not sure if it will do what I want, since according to the link, the periodic LSA refresh will still occur when there is a topology change.There is always the chance that I am missing something, so I will have to try it out and see how it behaves.

The link also triggered me to look into some other things, like flood-reduction and ospf database-filter. Intersting stuff. I don't know what they will do, but nontheless I will look into them.

Katerina

[katerina.dardoufa]

Ok! It seems that "ip ospf database-filter all out" does the trick! Unfortunately I only tried it out on a simulation lab, where I couldn't simulate BRI.

So I have to see, if the command is supported and if it works on a dialer interface.

[katerina.dardoufa]

The command "ip ospf database-filter all out" also works on a dialer interface, so I seem to have overcome my problem 

Hope this also helps somebody else!!!

Katerina