Multiple OSPF Process

[Arjun Dabol]

Hi

1. Can someone tell me Under what circumstances one would run multiple OSPF  process on a router ?

2. running muliple OSPF process is a must in PE-CE scenerio ?

thx

[Mark Malone]

Where I have seen it is on the ISP side on the PE routers you can have multiple processes enabled one for each customer

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/xe-3s/asr1000/iro-xe-3s-asr1000-book/iro-un-sw-vrfs.html#GUID-2130E2B3-78FD-4F4A-8BC5-879BF4ED319D

[Moh Mogh]

Hi,

1. OSPF with VRF to separate routing table for different purposes and having isolated routing, for example in case of mpls-vpn customers and having each routing table separated from the others.
There could be also some complex design demands, for example once I saw in a SP network that they had different PoP, and on each PoP link to the other, they had separated OSPF processes and were redistributing the processes into each other. I know, it's a mess!

2. OSPF is not a most, and you are able to use other routing protocols too. This depends on the requirements, for example Telco providers usually use BGP, which in turn could have more complexity for the customer but better manageability for the provider. In this regards, you take a look at this article: http://searchtelecom.techtarget.com/tip/Choosing-customer-MPLS-VPN-routing-protocols.

Regards,
Mohammad

[Joseph W. Doherty]

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Posting

#2, No, it's not a must.

#1 When you want to isolate or control route distribution between two different OSPF domains.  It's a bit rare to do this, especially within the same global or VRF routing instance.  Such an OSPF router doing such redistribution would be an ASBR, just as it might be if the same router was running OSPF and (RIP or EIGRP or BGP).