From: rsevier (rsevier@xxxxxxxxxxxxxxxxxxx)
Date: Mon Aug 20 2001 - 12:33:52 GMT-3
A- This is taken from CCO.
Reverse Path Forwarding (RPF)
RPF is a fundamental concept in multicast routing that enables routers to
correctly forward multicast traffic down the distribution tree. RPF makes
use of the existing unicast routing table to determine the upstream and
downstream neighbors. A router will only forward a multicast packet if it is
received on the upstream interface. This RPF check helps to guarantee that
the distribution tree will be loop free.
RPF Check
When a multicast packet arrives at a router, the router will perform an RPF
check on the packet. If the RPF check is successful, the packet will be
forwarded. Otherwise it will be dropped.
For traffic flowing down a source tree, the RPF check procedure works as
follows:
Step 1. Router looks up the source address in the unicast routing table to
determine if it has arrived on the interface that is on the reverse path
back to the source.
Step 2. If packet has arrived on the interface leading back to the source,
the RPF check is successful and the packet will be forwarded.
Step 3. If the RPF check in 2 fails, the packet is dropped.
Hope this helps,
Raymond
-----Original Message-----
From: Taz Kazam [mailto:taz_kazam@yahoo.co.uk]
Sent: Monday, August 20, 2001 8:12 AM
To: rsevier; Atakan SAN; ccielab@groupstudy.com
Subject: RE: RPF lookup failed stuff with auto rp
Guys,
Although slightly off the point. I just finished
reading up on RPF. From my reading RPF was used in the
context of the internet - How to avoid DoS attacks -
used on BGP edge devices.
Q? How is RPF used in relation to Multicasting ???
Thanks
Taz.
--- rsevier <rsevier@zealousolutions.com> wrote: >
Atakan - Check your unicast table. The RPF lookups
> are dependent on the
> unicast table and mroutes.
>
> Raymond
>
> -----Original Message-----
> From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com]On Behalf Of
> Atakan SAN
> Sent: Monday, August 20, 2001 7:46 PM
> To: ccielab@groupstudy.com
> Subject: RPF lookup failed stuff with auto rp
>
>
> Hi Group
>
> Very straightforward but hitting a strange issue
> sparse-dense mode all
>
> X3---------------- X2
> '
> '
> '
> '
> X1
>
> Testing auto-rp---> X3' s loopback0 192.19.27.7 is
> used for both
> announce and discovery messages for auto-rp
>
> I am having RPF lookup faileds as follows on X1
> 15:55:47: IP: s=192.19.27.7 (Serial0.12)
> d=224.0.1.39 len 52, RPF lookup
> faileds
> 15:55:47: IP: s=192.19.27.7 (Serial0.13)
> d=224.0.1.39 len 52, RPF lookup
> faileds
> 15:55:47: IP: s=192.19.27.7 (Serial0.12)
> d=224.0.1.40 len 52, RPF lookup
> faileds
> 15:55:47: IP: s=192.19.27.7 (Serial0.13)
> d=224.0.1.40 len 52, RPF lookup
> faileds
> X1#
> 15:56:47: IP: s=192.19.27.7 (Serial0.12)
> d=224.0.1.39 len 52, RPF lookup
> faileds
> 15:56:47: IP: s=192.19.27.7 (Serial0.13)
> d=224.0.1.39 len 52, RPF lookup
> faileds
> 15:56:47: IP: s=192.19.27.7 (Serial0.12)
> d=224.0.1.40 len 52, RPF lookup
> faileds
> 15:56:47: IP: s=192.19.27.7 (Serial0.13) d=224
>
> Thanks
> Atakan
> **Please
> read:http://www.groupstudy.com/list/posting.html
> **Please
> read:http://www.groupstudy.com/list/posting.html
>
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