RPF Type Multicast

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Sep 2nd, 2009
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RPF information for ? (10.10.10.10)

RPF interface: Loopback0

RPF neighbor: ? (10.10.10.10) - directly connected

RPF route/mask: 10.10.10.10/32

RPF type: multicast (connected)

RPF recursion count: 0

Doing distance-preferred lookups across tables


I have the above outputs on same routers with same ios but sometimes it shows rpf interface multicast. What does it mean?


regards

shivlu jain

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Peter Paluch Wed, 09/02/2009 - 01:56
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Hello Shivlu,


Quoting from the IP Multicast Routing Command Reference at:


http://www.cisco.com/en/US/partner/docs/ios/ipmulti/command/reference/imc_06.html#wp1077663


RPF type: Routing table from which this route was obtained, either unicast, MBGP, DVMRP, or static mroutes.


In your case, the router tells you that the information about this source is directly in the multicast routing table and that the source is directly connected.


Best regards,

Peter


shivlu jain Wed, 09/02/2009 - 03:44
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Thanks for reply.

Bu it should come via unicast.


regards

shivlu jain

Peter Paluch Wed, 09/02/2009 - 06:07
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Hi Shivlu,


Hmmm... Is that loopback configured in any special way?


Best regards,

Peter


Laurent Aubert Wed, 09/02/2009 - 19:21
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Hi Shivlu,


The change is due to the new Mu-RIB implementation on 7600 which provides a dedicated table for RPF.


So the output just told you, the RPF is done using this table.


You can see it with show ip route multicast.


This new implementation is related to MTR.


http://www.cisco.com/en/US/docs/ios/mtr/configuration/guide/multi-top_rtng_ps6922_TSD_Products_Configuration_Guide_Chapter.html#wp1053994


HTH


Laurent.

shivlu jain Wed, 09/02/2009 - 22:46
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Hi Laurent


Thanks for the reply. I think it is the same as cef is created from RIB. In this case Mu-MTR is created from RIB.


Second question why this is required, is it going to enhance the performance of box? What are the various advatages of using Mu-MTR?


Third question:- I have not enabled the topology command in global then I should not get the rpf type: multicast output.



regards

shivlu jain





Laurent Aubert Thu, 09/03/2009 - 06:30
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Not created but filled from RIB.


The behavior is the following:


1- Multicast MTR is not configured


The MuRIB is still created and used for RPF but the legacy RPF rules apply so the table is filled in a way to be compatible with those rules.


2- Multicast MTR is configured


By default only directly connected routes and routes from multicast protocols (static, mBGP, mIGPs) will be installed in the MuRIB. You can also import unicast routes from any configured topology or even configure which topology you want to use for RPF (bypass the MuRIB in this case).

Longest-match rule applies by default.


So main advantages are:


- Single place where we have all the routes we want to use for RPF

-> single lookup vs several with the legacy implementation.


- Easier to implement non-congruent multicast topologies.


- Support mIGP's


- Consistent with XR (already default behavior)



HTH


Laurent.

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