LinuxSA Mailing list archives

  From: Mark Newton <newton@atdot.dotat.org>
  To  : Jason Tan <jason@rebel.rebel.net.au>
  Date: Thu, 7 Dec 2000 11:16:31 +1030

Re: "Host based" routers and BGP

On Thu, Dec 07, 2000 at 10:46:54AM +1030, Jason Tan wrote:

 > > You have assumed a middle to high end scenario for routing. What scope is
 > > Jason looking for? It goes without saying that for high capacity systems
 > > you use the best you can get that is optimised for that role. The same
 > > goes for database servers, firewalls, transaction systems and so on.
 > 
 > MMy understadnign is that it is not really the size of the network you are
 > rotuign for ie how many addresses are in your network that is the issue to
 > complxiety and correctbness(it may be with thoutghput however but for my
 > case I am not inerested in throughput).
 
Depends.  You need to be of a certain size to use BGP;  Almost everyone
will refuse to accept route advertisements if their prefix is too long
(i.e.: you'll have no problems with announcing a /20 route, but don't
even think about anything with a prefix longer than 24 bits).

Generally speaking, you can't announce any prefixes larger than the 
allocation you'd have received from APNIC unless you have special 
arrangements with your upstreams (basically your upstreams would need 
to know that they can aggregate your announcement with others, so they'll
be advertising a larger network to their peers even if your advertisements
are for small networks).

 > Ratehr I get the impression that the problems with correctness and
 > complexity are defined by your external realtionships.
 > Ie how many neghbours you have.
 > Or basically are you multijhomed?

If you're not multihomed with portable address space, there's absolutely no 
value in running BGP.

 > And if so then how you swap routing info?

BGP :-)

You'd need an AS number (either from APNIC, or via a private AS number if
you have special arrangements with your upstreams).  Then you basically
tell BGP about which networks you have, who you want to announce them
to, and what to do with inbound announcements, and let your BGP software
handle the rest.


   - mark

--------------------------------------------------------------------
I tried an internal modem,                    newton@atdot.dotat.org
     but it hurt when I walked.                          Mark Newton
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