From: Fred Nielsen (fred_nielsen@xxxxxxxxxxx)
Date: Sat Jul 29 2000 - 21:51:23 GMT-3
I would like to hear the opinions of the group on the synchronization
rule, which states *something* like: a BGP router will not forward an
externally learned route to another external peer until the route is
also present in that router's IGP as well.
The Halabi book touches on this, but didn't spend enough time for me
to really understand the intent behind the rule, other than to prevent
routing loops inside an AS. Because many typical configurations out
there do not redist BGP routes into IGP's, you see the "no
synchronization" command employed fairly often. Why is sync turned on
by default in the IOS? Is it part of the specification perhaps?
Also, referring to "external peer" above, this really means separate
router entities running IBGP within an AS, right? Not between EBGP
peers, where the rule doesn't apply..
And one more question, does the IGP route have to match precisely, or
can a less specific route do the trick? In other words, can the
presence of 10.0.0.0/8 in the IGP allow BGP to forward a 10.1.0.0/16
route?
Hoping all this makes sense.
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Fred Nielsen [fred_nielsen@hotmail.com]
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