"E2" Routes Decommission

Unanswered Question
Apr 21st, 2008

Hello Experts,

We are planning to remove all the "E2" Rotues from our Backbone of Large Scale Service Provider Network and would like to know what all the Measures to be taken care Prior / Post to the Activity.

Please recommend with the List of Steps proposed to be Measured for the successful 'E2' Routes Removal, so that by having 0% impact to the Network and all Others.

Thanks in Advance for all your HELP

Best Regards,

Guru Prasad R

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Edison Ortiz Mon, 04/21/2008 - 05:23

How are you planning to 'remove' these "E2" routes ?

Is the plan to avoid any reachability to/from those destinations or is the plan to use "E1" or a default route ?

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Edison.

guruprasadr Mon, 04/21/2008 - 05:35

HI Edison,

Thanks for your POST.

I forgot to add 1" more important point. In my Network Currently "OSPF" is handling more than 20,000 E2 Routes and i know there are some limitation the amount of "E2" Routes the OSPF can handle in a Network as per CISCO.

Because of more number of E2 Routes in the OSPF Table, i am afraid that my OSPF Convergence time may get impacted since i have already crossed the supported limit on OSPF Protocol.

We are planning to reduce the E2 Routes in OSPF Table and carry the same in BGP Protocol, since it has more efficiency to carry even the Internet Routing Table Size with higher performance.

Looking forward for your Expertise. Thanks in Advance for your Answers.

Best Regards,

Guru Prasad R

Edison Ortiz Mon, 04/21/2008 - 05:43

In short, you are doing a dynamic protocol migration.

The best way of doing it, is incorporating both protocols on the respective routers. If you are doing eBGP *and* announce the same networks, you will see your routing table populating the information via BGP instead of OSPF.

If you are doing iBGP, then you will need to either play with the AD on iBGP (to be preferred over OSPF) and increase the AD on OSPF.

Either way, I recommend capturing your routing table today and then perform a 'windiff' (http://en.wikipedia.org/wiki/WinDiff)

between what the output looks now vs what it will look when you introduce those routes with another protocol.

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