Which option is used as a loop prevention mechanism to support MPLS VPN customers with
multihomed sites?
A.
BGP down bit
B.
sham links
C.
AS override
D.
SOO extended BGP community
E.
allowas-in
Explanation:
http://www.cisco.com/en/US/docs/ios/12_4t/12_4t11/htbgpsoo.html
Site of Origin BGP Community Attribute
The site-of-origin (SoO) extended community is a BGP extended community attribute that is used
to identifyroutes that have originated from a site so that the readvertisement of that prefix back to
the source site can beprevented. The SoO extended community uniquely identifies the site from
which a router has learned a route.BGP can use the SoO value associated with a route to prevent
routing loops.