Different OSPF Process ID For Interconnect between 2 OSPF Domain

[tckoon]

Hi all,

Please refer to attached diagram. Currently the OSPF network consist of 2 segment route via static route.

One is AREA 0 and another AREA 10.

Both network are seperate entity, only static route to route between 2 networks.

But the static route do not provide the dynamically and flexibility, I plan to run routing between 2 networks via VLAN160 and VLAN162.

I still want to manitnace it was 2 different OSPFrouting domain.

Can I  run OSPF with differrent OSPF porcess ID

[Peter Paluch]

Hello,

The OSPF process ID is a locally-significant value. Even if you configured your network as you suggested in the attached PDF file, i.e. PID 100 on the ISPSW1 and ISPSW2 routers, and PID 200 on the SW-A1 and SW-A2 routers, it would still form a single OSPF domain. You would actually need to run two separate OSPF processes on the ISPSW1 and ISPSW2 - one with PID 100 as you do now with no changes to it (assuming it is not run towards the customer), and another with a different PID, that would be activated on the interface V160 and 162 towards the SW-A1 and SW-A2 switches.

Please note, however, that if you plan to redistribute the networks from one OSPF process into another in some future, it would be better to maintain just a single process, and better use areas, area filters and LSA limits (max-lsa) to keep a relative independence of the two domains in your network. Redistributing between OSPF processes is somewhat cumbersome and has to be configured cautiously.

Best regards,

Peter

[tckoon]

Hi Peter,

Based on my requirement ,if I configure V160 and V162 with OSPF aera 50 and process ID of 300 at ISPSW1 / ISPSW2 and SW-A1 /SW-A2.

Will route exhange between 2 network ? or I need to redistribute between OSPF process 100 and 300 for ISPSW1/ISPSW2  and process 300 and 200 at SW-A1/SW-A2.

[Edison Ortiz]

No redistribution is needed.

[Atif Awan]

tckoon@hp wrote:
Hi Peter,
Based on my requirement ,if I configure V160 and V162 with OSPF aera 50 and process ID of 300 at ISPSW1 / ISPSW2 and SW-A1 /SW-A2.
Will route exhange between 2 network ? or I need to redistribute between OSPF process 100 and 300 for ISPSW1/ISPSW2  and process 300 and 200 at SW-A1/SW-A2.

With this configuration you are introducing a third OSPF domain. Only those routes will be exchanged between the two networks that you make part of the OSPF process 300. If you want end to end reachability then there is no way around redistribution. That being said I will side with Peter that redistribution between two OSPF Processes may end up being a bit complicated in the long run.

If your intention is to maintain separation between the two networks and introduce a dynamic mechanism of route exchange have you considered using BGP instead?

Atif

[tckoon]

Hi Atif,

Have no plan of running BGP, you can refer to my update diagram. Previous diagram I am not showing detail about BGP and ISP section.

The SW-A1 and SW-A2 is consider to be internal private network, the ISPSW1 and ISPSW2 is public Internet facing.

That is why I do not want to "join" them together, one good way is static route but disadvantage is it not so dynamic'flexsible when come to failover/redudancy of the network.

In my case I would like to have default route advertise to internal network, and internal network advertise 113.10.0.0/16 to ISPSW.

I also like to control routing to prefer SW-A > ISPSW1 path, in case this active path failed, it can automatically failover over to SW-B>ISPSW2 path.

This I think it can only achived via dynamic routing.

I think I need to try it out in Dynagen lab, use redisribution between OSPF process and control the route to be advertised via route-map.

Do you think it works ? I not really care about complication as far it works.

Regards

" that is why ccie lab  tend to have such complicated "redistribution here and there" questions

btw i am not ccie....

[Atif Awan]

tckoon@hp wrote:
Hi Atif,
Have no plan of running BGP, you can refer to my update diagram. Previous diagram I am not showing detail about BGP and ISP section.
The SW-A1 and SW-A2 is consider to be internal private network, the ISPSW1 and ISPSW2 is public Internet facing.
That is why I do not want to "join" them together, one good way is static route but disadvantage is it not so dynamic'flexsible when come to failover/redudancy of the network.
In my case I would like to have default route advertise to internal network, and internal network advertise 113.10.0.0/16 to ISPSW.
I also like to control routing to prefer SW-A > ISPSW1 path, in case this active path failed, it can automatically failover over to SW-B>ISPSW2 path.
This I think it can only achived via dynamic routing.
I think I need to try it out in Dynagen lab, use redisribution between OSPF process and control the route to be advertised via route-map.
Do you think it works ? I not really care about complication as far it works.
Regards
" that is why ccie lab  tend to have such complicated "redistribution here and there" questions 
btw i am not ccie....

It is not about whether it will work or not. Yes it can be made to work but the complexity comes from the fact that multiple OSPF processes will have the same AD and if a route is available via two processes the actual route insertion (in RIB) behavior is indeterministic. You can use route-maps to properly control the route redistribution behavior but just because you can do it does not mean it is the thing you should be doing .

That being said are ISPSW1 and ISPSW2 in your administrative control? If yes then I would merge the two OSPF domains into one and secure your edge devices. If ISPSW1 and ISPSW2 are not in your administrative domain then I will prefer to run BGP with them.

Atif

[lgijssel]

Opposite to eigrp, there is no requirement for matching process id's with ospf.

Exchange of routing updates depends on correct and consistent definition of the area's via the network statements.

regards,

Leo

[Edison Ortiz]

Sure, OSPF PID is locally significant.