EIGRP backdoor link on MPLS VPN and multiple SoO values

According to paragraph 2) on page 2545 of INE CCIE R&S Lab Workbook Volume
1 (CCIEv4.0), when configuring PE routers of a multi-homed sites with
different SoO values, an additional SoO interface should be configured on
the CE routers with the backdoor links " to prevent routing loops.

Diagram:

PE1 -------------P--------P------------------PE2
 | |
 | |
SoO=100:1 SoO=100:2
 | |
 | |
CE1--SoO=100:1----------SoO=100:2-CE2

Questions:

How can a CE (acting as a backdoor) filter updates based on the site of
origin since the CE is not running
MBGP ?

I have taken a network capture of traffic on the backdoor link, I do not
see any extension in EIGRP carrying the SoO attribute ...

Any input welcome.

Thanks

Pierre-Alex

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Received on Mon Feb 13 2012 - 13:10:53 ART