Community NO-EXPORT

[Dave Cahill <dcahill () salesforce com>]

Community NO-EXPORT 

I have AS1 connected to AS2 via two different paths and different routers

|-------------------|         |--------|
|                   |---------|        |-----OTHERS
|       AS1         |         |  AS2   |
|  192.168.0.0/16   |         |        |
|                   |---------|        |-----OTHERS
|-------------------|         |--------|


I advertise my class B range from AS1 for example 192.168.0.0/16 on both
routers but
to achieve some load-sharing I addvertise 192.168.0.0/17 on one router and
192.168.128.0/17 on the other router as well.

I setup a community NO-EXPORT for the /17 so AS2 won't advertise them out to
other AS's.

The question
In AS2 BGP selects the best route and /17 should be selected because of the
longest
match rule.  BGP places the /17 in its routing table.  BGP should only
UPDATE the other
IBGP Peers with its routing table entry (IE Each router won't send it's
entire BGP database).
So if the /17 will be sent to other IBGP with the community NO-EXPORT how do
other AS's learn
about the /16 ?



Dave Cahill