North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: Confussion over multi-homing

  • From: John Fraizer
  • Date: Thu Sep 14 20:40:58 2000

On 14 Sep 2000, Sean Donelan wrote:

> On Thu, 14 September 2000, Brantley Jones wrote:
> > The problem is GETTING a /20 from anybody.  We recently tried and could 
> > only get a /23 (being a small start-up).  BUT, that /23 is (apparently) 
> > globally routable because of peering agreements with L3 and UUNET.  Our /23 
> > prefix has yet to be filtered by anybody.
> It could be filtered now.  You just won't find out about it until you try
> to reach a particular site, or they try to reach you.
> There is no practical way to test if an address is being "globally routed."
> You could try testing every address in your route table, but there is no
> assurance your route table is complete.


They won't see it even if their /20 announcement is being filtered as long
as their upstream is listening to it.  (Upstream being the carrier they
obtained the /20 from.)  This is because even though some ISP/NSPs may not
listen to the specific /20 announcement, I haven't found any who will
ignore a /19 or /17 announcement for the master block.  As long as they
know how to get to that block, and teh "upstream" knows how to get to the
/20, the route filtering isn't going to be apparent at all... Until the
time that the "upstream" has connectivity issues.

John Fraizer
EnterZone, Inc

-- Support your government, give Echelon / Carnivore something to parse --
classfield  top-secret government  restricted data information project CIA
KGB GRU DISA  DoD  defense  systems  military  systems spy steal terrorist
Allah Natasha  Gregori destroy destruct attack  democracy will send Russia
bank system compromise international  own  rule the world ATSC RTEM warmod
ATMD force power enforce  sensitive  directorate  TSP NSTD ORD DD2-N AMTAS
STRAP warrior-T presidental  elections  policital foreign embassy takeover