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Re: shim6 @ NANOG (forwarded note from John Payne)
marcelo bagnulo braun wrote:
Wouldn't the hosts in X and Y have two IPv6 addresses?
Thus BGP itself at site X wouldn't know that B:Y and D:Y is the same
host, hence BGP wouldn't compare them to find the best.
yes, but i think could work anyway
I mean, suppose that we are performing source address rewriting by the
multihomed site exit routers
Now suppose that intra site routing is performed based solely in the
destination address (just as it is in the current paradigm)
Assume that the multihomed site obtains BGP feed through both of its
Now, based on the BGP information obtained, the intra site routing will
preffer one or other exit to reach a given destiantion.
So, when a host within the multihomed site sends a packet to that
destination the exit route will be determined by this BGP information
hence the policy information pushed by the transit ISPs can affect the
intra site route selection
Since the site exit routers can rewrite the source address, they will
select the appropriate source prefix
My response to Iljitsch was about his assertion about the current
workings of shim6 - not taking into account any hypothetical extensions
like router rewriting about locators.
But even with such a hypothetical extension, there would be nothing in
BGP that would know that the B:Y and D:Y address prefixes are for the
same site, hence nothing in BGP that would compare the metrics (AS path
length or whatever) for the routes to those two separate prefixes.