(Re)export unreachable routes via BGP.

4 Nov 2018

      Is it possible to (re)export unreachable routes via BGP?

I have established a pair of BGP neighbor sessions with Team Cymru Route 
Servers, both of which are receiving unreachable prefixes, namely 
bogons, like they should be.  I would like to (re)export said prefixes 
to a different machine that is not able to form a BGP neighbor session 
with Team Cymru (for various reasons).

All attempts thus far have resulted in the BGP neighbor session with the 
3rd test machine not (re)exporting any unreachable routes.  I can 
(re)export other routes without a problem.  It looks to me like BGP is 
rejecting the the routes (I think) because they are unreachable.

"show route table bogons" works as expected, and shows the routes 
received via both of the BGP neighbor sessions with the Team Cymru Route 
Servers.  Similarly, I can see the unreachable routes in the proper 
table from Linux.

Thank you in advance for any help / enlightenment that you can provide.

--8<--
bird> show protocols all grant
name     proto    table    state  since       info
grant    BGP      bogons   up     21:12       Established
   Description:    Feed to Grant at home
   Preference:     100
   Input filter:   REJECT
   Output filter:  ACCEPT
   Routes:         0 imported, 0 exported, 0 preferred
   Route change stats:     received   rejected   filtered    ignored 
accepted
     Import updates:              0          0          0          0 
      0
     Import withdraws:            0          0        ---          0 
      0
     Export updates:           3031       3031          0        --- 
      0
     Export withdraws:            0        ---        ---        --- 
      0
-->8--

--8<--
filter cymru_bogons_import {
    bgp_community.add((REDACTED,888));
    #dest = RTD_BLACKHOLE;
    accept;
}

filter cymru_bogons_export {
    reject;
}

protocol bgp cymru1 {
    description "Team Cymru Bogons Route Server #1";
    import filter cymru_bogons_import;
    #export filter cymru_bogons_export;
    #import all;
    export none;
    multihop 255;
    local as REDACTED;
    neighbor REDACTED as REDACTED;
    source address REDACTED;
    table bogons;
}

protocol bgp cymru2 {
    description "Team Cymru Bogons Route Server #2";
    import filter cymru_bogons_import;
    #export filter cymru_bogons_export;
    #import all;
    export none;
    multihop 255;
    #password "FIXME";
    local as REDACTED;
    neighbor REDACTED as REDACTED;
    source address REDACTED;
    table bogons;
}

protocol bgp grant {
    description "Feed to Grant at home";
    import none;
    export all;
    multihop 255;
    local as REDACTED;
    neighbor REDACTED as REDACTED;
    source address REDACTED;
    table bogons;
}
-->8--

-- 
Grant. . . .
unix || die

(Re)export unreachable routes via BGP.

Grant Taylor