Require suggestion for failover

Answered Question
Jun 30th, 2010

Hi ...

I have a Hub - Spoke scenarion...Like..

Datacenter located at Mumbai having primary Rel with BGP and secondary Tata with static routing.(Both Rel and tata MPLS Connectivity).

Branches are spreads all over india having same primary Rel and secondary Tata with both static routing.If Rel goes down I manually change staic routing for Tata.

For avoding manual intervention i want to configure OSPF.For that i want some input....

1) What i have to configure at Mumbai Datacenter.

2) Branch end configuration

3)What is service provider role in this?

4) Presently we are using 2800 series router at both Mumbai and Branches.Is it sustain?

Any help is highly appreciated...Pls find the attached net diag..

Thanx...

Attachment: 
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Correct Answer by Chetan Kumar Ress about 6 years 5 months ago

Hi Arun

Frist of all  you need to decide that what Dynamic routing protocol you will use.

Accourding to me...

1] Fro REL you shoud use BGP for all location & HO.

2] For TATA you should use OSPF for all location & HO.

OR

3] For TATA you should use BGP for all location & HO

It is not possible to use HO to TATA as BGP & All TATA location OSPF. Because SP won't agree with this kind of services.

Case1] If you are using BGP for Both SP then you should use Weight (BGP Att ) for route selection.

Case2] If you are using OSPF for TATA & BGP for REL then AD will take care for route Selection.

If at branch Rel link down, branch traffic will automatically shifted to tata over OSPF.but what about return traffic?

at HO due to both the links up, which path it will take? Rel or Tata?

Here If your REL link goes down then the location prefer OSPF route and the return traffic will use TATA OSPF ( from DC ). Because in DC  you won't See the route for that location in BGP REL link . ( Since the BGP REL link is down for that location So no advertisement will come here)

Same will apply for every senario ( If DC link fail or REL link fail in locaiton )

Regards

Chetan Kumar

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vladimirsaltao Wed, 06/30/2010 - 08:40

Some quick thoughts:

1) Use ospf for primary links, you have to work with your ISP in doing this, for backups links use statics routes with a bigger metric

2) use ospf with both links, use ospf cost to ensure primary link is used over backup link

arjunsawant Wed, 06/30/2010 - 09:10

Hi...

Thanx for ur quick reply....

But i have one query regarding area.....Is it right way to configure that..

1) if i configured Area 0 for Mumbai and Another same area for all the branches OR

2) if i configured Area 0 for Mumbai and four diff areas for 5-5-5-5 branches  OR

3) if i configured Area 0 for Mumbai and diff area for each branch OR

4) Mumbai and branches are configured is Area 0 ?

>>>>>Thanx..

Chetan Kumar Ress Wed, 06/30/2010 - 09:09

Hi Arjun

To achive this auto fail-over you have to many opitons.

1] Simply you can configure IP SLA with Track option in all locaitons. For more detail http://www.ciscoblog.com/archives/2008/08/dynamic_failove.html

Note : But for IP SLA in your senario you should use Dynamic routing protocol for TATA link between HO & TATA not for locations.

2] You can run dynamic routing protocol for all locaitons for TATA link or Reliance link.

For Example :  For Rel you can use EBGP for all locaiton & HO .

                      For TATA you can use ospf for all locaiton & HO.

Here in you HO router the primary will be REL because EBGP AD is 20 & ospf is 110.

So in your router you will see the two routes for every location. One from BGP & other from OSPF.

1) What i have to configure at Mumbai Datacenter.

----> You should configure any dynamic routing between SP & DC for IP SLA.

----> If you are going with dynamic routing for all locaiton the also you nee to configure OSPF for TATA.

2) Branch end configuration

----> For IP SLA , Configure only IP SLA with track no dynamic routing.

----> For Dynamic routing configure ospf for TATA & BGP for Reliance.

3)What is service provider role in this?

---->For Dynamic routing  TATA should agree to provide dynamic routing over MPLS cloud ie OSPF .You have to disscuss with you SP

----> For IP SLA you have to disscuss with TATA to provide dynamic routing between DC & TATA no for locaiton .

4) Presently we are using 2800 series router at both Mumbai and Branches.Is it sustain?

----> 2800 is good for managing every thing in your senario. ( Check the memory in you have too many locaiton)

Regards

Chetan Kumar

arjunsawant Wed, 06/30/2010 - 09:55

Hi Chetan......

                    Thanx for u'r reply...

I want to configure OSPF only for Rel and keep static routing for tata.Without IP Sla is it possible for failover?

If yes then what could be the answers of 4 questions.

Thanx once again....

Chetan Kumar Ress Wed, 06/30/2010 - 10:03

Hi Arjun

Accourding to me you can't achive auto failover if you use OSPF with REL & Static with TATA .

Please go through below senario :

1] For Example if you Both REL link fail in DC then how reverse traffic will flow .( If you are communicating from DC to Locations)

2] If you REL link fail in locaiton & it use TATA in that case then how your reverse traffic will flow from DC. ( In case you are communicating from Location to DC)

As per my understanding you can't achive failover using one dynamic routing & one Static routing. . Because you have Two link in very location & DC.

You have to use any Tech to manipulate the route.

Regards

Chetan Kumar

arjunsawant Wed, 06/30/2010 - 11:37

Hi chetan.....

Thanx once again...I got your point.

But in previous post,

1) What i have to configure at Mumbai Datacenter.

----> You should configure any dynamic routing between SP & DC for IP SLA.

----> If you are going with dynamic routing for all locaiton the also you nee to configure OSPF for TATA.

.......Can we configure BGP between DC and SP(Tata).

And

2) Branch end configuration

----> For Dynamic routing configure ospf for TATA & BGP for Reliance.

........Can we configure OSPF for both Rel and Tata.

Pls dont hesitate if I asking any silly question, Because i want to clear each and everything before implementation.

Query example: Assume at HO both Rel and Tata link up.Branch both Rel and Tata link up.

case I: If at branch Rel link down, branch traffic will automatically shifted to tata over OSPF.but what about return traffic?

            at HO due to both the links up, which path it will take? Rel or Tata?

[ Mumbai-BGP------------------BGP-REL-OSPF-----------------------OSPF-Branch

                BGP------------------BGP-Tata-OSPF----------------------OSPF-Branch]......Is it work?   OR

[ Mumbai-BGP------------------BGP-REL-BGP-------------------------BGP-Branch

                OSPF----------------OSPF-Tata-OSPF--------------------OSPF-Branch]......Is it work?  

Thanx a lot.....for understanding me..

Correct Answer
Chetan Kumar Ress Wed, 06/30/2010 - 12:03

Hi Arun

Frist of all  you need to decide that what Dynamic routing protocol you will use.

Accourding to me...

1] Fro REL you shoud use BGP for all location & HO.

2] For TATA you should use OSPF for all location & HO.

OR

3] For TATA you should use BGP for all location & HO

It is not possible to use HO to TATA as BGP & All TATA location OSPF. Because SP won't agree with this kind of services.

Case1] If you are using BGP for Both SP then you should use Weight (BGP Att ) for route selection.

Case2] If you are using OSPF for TATA & BGP for REL then AD will take care for route Selection.

If at branch Rel link down, branch traffic will automatically shifted to tata over OSPF.but what about return traffic?

at HO due to both the links up, which path it will take? Rel or Tata?

Here If your REL link goes down then the location prefer OSPF route and the return traffic will use TATA OSPF ( from DC ). Because in DC  you won't See the route for that location in BGP REL link . ( Since the BGP REL link is down for that location So no advertisement will come here)

Same will apply for every senario ( If DC link fail or REL link fail in locaiton )

Regards

Chetan Kumar

arjunsawant Wed, 06/30/2010 - 23:37

Hi chetan....

Thanx a lot for clearing my doubt....I will implement and revert to u..

Before that one more query is that,

According to U if I use BGP for Rel and OSPF for Tata,what will be the best design for OSPF..

1) if i configured Area 0 for Mumbai and Another same area for all the branches OR

2) if i configured Area 0 for Mumbai and four diff areas for 5-5-5-5 branches  OR

3) if i configured Area 0 for Mumbai and diff area for each branch OR

4) Mumbai and branches are configure is Area 0 ?

And In your scenarion is it require to configure IP Sla or routing protocol metric will take care?

Thanx.......

Chetan Kumar Ress Thu, 07/01/2010 - 07:56

Hi

For OSPF area design you have to involve your SP.

SP will act as a Area0 & ABR for all locaiton .

Best design for ospf or any dynamic routing protocol is to take any key input from you organization where you can identify any location easily & you can do summarization.

For Exp : You can use ospf as per States.

And In your scenarion is it require to configure IP Sla or routing protocol metric will take care?

In your network if you are not using Dynamic routing then you requried IP SLA & if you are going with Dynamic Routing then Metric will take care of Primary & Sec.

Regards

Chetan Kumar

arjunsawant Fri, 07/02/2010 - 00:51

Hi Chetan.....

Thank U Very much....for such a kind  help...

Arjun...

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