Hi. I'd like to point something out: by not tieing IGP to EGP,
folks have a responsibility.
Ideally, the purpose of BGP is to announce the availability of
networks -- if your network can't deliver traffic to a remote
network, you shouldn't be announcing via BGP.
Unfortunately, we don't live in an ideal world. To improve
stability of the global BGP mesh, folks have decided not to tie
BGP to their IGP -- and personally, I think that's a darned good idea.
But this decision has a cost: when making a change that will
affect routing (such as a router upgrade), these folks can't rely
on IGP to straighten out their network's reachability matrix. It
seems to me that responsible folks would emply manual
intervention to ensure that their BGP announcements would
match the state of their network.
For instance: when upgrading a router, I think the responsible
folks would determine the the "top" of that router's topology,
shut down BGP into that topology, do the upgrade, and then
reenable BGP.
In other words, if you're running your BGP on "manual," and you
manually do stuff to affect your network, please make the manual
changes to ensure BGP knows about the state of your network.
This only means one "flap", and it will make the world a nicer
place.
-Scott
