Reducing the delay time in Static and OSPF routing.

Unanswered Question
Oct 22nd, 2009

We have two sites coimbatore and Hyderabad, we have 1 Internet router and 1 MPLS router at each site.

In Coimbatore static router is running among core, internet and MPLS router.

In Hyderabad OSPF is running among core, internet and MPLS router.

In both the sites MPLS link is using as a primary link and internet router is using as a backup.

Now, the customer needs to switch the traffic from

MPLS router to Internet router [if the MPLS router goes down] with minimum delay.

At present, it is switching to INternet router with 35 sec approx. delay.

Is it possible to decrease the delay time under static and OSPF routing?

Diagram is duly attached.

Attachment: 
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Jerry Ye Thu, 10/22/2009 - 09:25

There is no timer for static route. However, with OSPF, you can speed up the convergence time by changing the timer to sub-second. But this might cause large amount of SPF calculation (high CPU). You need to plan it out carefully.

The command you can use in OSPF is

ip ospf dead-interval 1 minimal hello-multiplier 4

This will give you 250ms hello interval.

http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_osp1.html#wp1014268

Regards,

jerry

Joseph W. Doherty Thu, 10/22/2009 - 10:35

As Jerry notes, adjustment of OSPF hello parameters can decrease OSPF convergence. In the next chapter of same document, you'll see the "ip ospf hello-interval" command documented. Likely you might be running at the nonbroadcast default of 30 seconds. Either using this command or Jerry's should decrease detection of loss of OSPF neighbor.

There are other OSFP options (e.g. timers) for decreasing OSPF convergence, but unless you're attempting to get subsecond times, these might be ignored. What techniques and commands you need depend on how fast you are trying to get OSPF to converge. (You might find even a 1 second hello a dramatic improvment.)

As to static routes, if your platform supports it, you might look a reliable static routing (http://www.cisco.com/en/US/docs/ios/12_3/12_3x/12_3xe/feature/guide/dbackupx.html).

[edit]

PS:

You can find more information about fast OSFP convergence in: http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6554/ps6599/ps6629/prod_presentation0900aecd80310f6d.pdf

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