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[6bone] no-export community not being honored

People not honoring "no-export" when redistributing routes:

109 announces 2002::/16 tagged with the "no-export" well-known community.

    3ffe:c00:8023:4::1 from 3ffe:c00:8023:4::1 (
      Origin IGP, metric 0, localpref 100, valid, external, best
      Community: no-export
      Last update: Fri Aug  2 23:13:51 2002

The problem is, it appears that many people wipe this out, probably with "set community
none" or "set community nnnn:nnnn" without the "additive" modifier.

Here are a few examples of folks redistributing 109's "no-export" tagged route:

  6175 109
    3ffe:2900:d:e::1 from 3ffe:2900:d:e::1 (
      Origin IGP, metric 0, localpref 100, valid, external
      Last update: Sat Aug  3 00:10:51 2002

   6342 109 (history entry)
     2001:750:E::5 from 2001:750:E::5 (
       Origin IGP, localpref 100, external
       Dampinfo: penalty 10785, flapped 459 times in 15:32:04

   33 109
     3FFE:1200:1002:1::81 from 3FFE:1200:1002:1::81 (
       Origin IGP, localpref 100, valid, external

I know... Someone is going to say "This is the 6bone.  We're
experimenting.  We're learning."

OK.  Here is a lesson: When you receive a prefix that has no-export
tagged, you don't export it.  If you're running a route-map that clears
communities, it might be a good idea to NOT clear the
(local-AS|no-advertise|no-export) community.  It's being set by the origin
AS for a reason.

John Fraizer              | High-Security Datacenter Services |
EnterZone, Inc            | Dedicated circuits 64k - 155M OC3 |
http://www.enterzone.net/ | Virtual, Dedicated, Colocation    |