[c-nsp] delay eBGP sessions on startup?

[Bill Desjardins]

Hi Gert,

just an idea. I have not tried this and it may also not fit your
application... this is on sup2's (SXF17)

in my tiny network I have several route reflectors which handle only
my customer assignements. nice and small for ibgp convergence.

the idea is that the border routers peer with the ibgp RR's and use a
bgp conditional statement to advertise your aggregate upstream only
upon matching a 'trigger route' received from the ibgp RR. I am no bgp
expert and am unsure if the received routes are sorted or not, but if
so, you could add a max IPv4 address like 254.254.254.254/32 to place
it at the end of the received update. if the updates are not reliably
sorted, this is probably all for not though.

then with a bgp conditional such as:

neighbor x.x.x.x advertise-map EBGPOUT exist-map IBGPDONE

you would only advertise out after your IBGP session is near end at
least giving you the best chance to avoid blackholes.  you should also
have solid reliability to multiple RR's to keep it stable.

granted a knob would be nice, but at least this method can be
centralized and uses commands meant to do this anyway. all your doing
is adding an internal 'trigger route' to signify ibgp is about done so
send out ebgp advertisements when ya get a chance :)

Bill