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Re: /24s run amuck

  • From: Patrick W.Gilmore
  • Date: Tue Jan 13 16:15:13 2004 
On Jan 13, 2004, at 3:58 PM, Steve Francis wrote:


Patrick W.Gilmore wrote:



On Jan 13, 2004, at 2:19 PM, Steve Francis wrote:




I'll take some education - given two POP's, different upstream ISPs
at each POP, and a desire to have traffic for specific networks
(/24) enter a specific POP, can that be done without de-aggregation?

We are not doing this ourselves - we're not yet big enough to have
our own aggregate blocks, but if we did, we could not just announce
a /20 at each POP, and transit the traffic back to the appropriate
datacenter ourselves. We're an ASP, and do not have real links
between POP's, only VPN's.



If we used consistent upstreams at each POP, we could do it by
announcing specific /24's with no-export communities, but a
consistent set of ISPs are not available at each of the colo's we
are in.



Is there some other trick I'm missing?





If you can't take the traffic from Site A to Site B, why are you
announcing the /24s to the world? Why not just use a /24 from the
upstream in each location and not force everyone else on the Internet
to see your /24 which only has one path?



It doesn't have just one path. Multiple (different) ISPs at each
location.



Then this is just two instances of the same problem: You have a site
with a /24 and multiple upstreams. How do you aggregate?



Answer: You don't. This is the type of deaggregation which is a
"necessary evil". And, IMHO, why filtering on /20 (or whatever) is a
Bad Thing. You have just as much right to multiple upstreams as the
"big guys". Again, IMHO. Many people on this list - all of them
running large networks, you will notice - would argue otherwise. They
seem to think that if you do not have a /16, you should not have
multiple upstreams.



Fortunately, the market, and the Internet, has clearly spoken.
Unfortunately, they may have spoken a little too loudly, and now we
have "/24s run amuck". :)



--

TTFN,

patrick