This is just one of the many reasons why we need ARIN proposal 2002-3 to be approved. So that small networks that wish to multihome don't have issues with networks filtering out their /24 along with all the other garbage /24's that are announced. http://www.arin.net/policy/2002_3.html If you support 2002-3 I urge you to get on the ARIN Public Policy Mailing List (PPML) and voice your opinion. http://www.arin.net/mailing_lists/index.html Forrest -----Original Message----- From: H. Michael Smith, Jr. [SMTP:michael@awtechnologies.com] Sent: Wednesday, October 15, 2003 4:24 PM To: 'Phil Rosenthal'; 'John Palmer' Cc: nanog@merit.edu Subject: RE: Pitfalls of annoucing /24s What about the /24's that many ISPs (especially tier 2-3) are assigning to multi-homed customers? What about an IX or "critical infrastructure providers" that may be issued a /24 from ARIN (Policy 2001-3)? Although it may be rare that a large aggregate would become unreachable to a "large" network, doesn't the possibility exist that a customer with a /24 would become unreachable (to some) due to the aggregate dropping out even though the /24 should still be reachable? That scenario may not be very likely, but the question of assymetric routing and one's ability to balance traffic become issues. Assigning a lower preference to /24's would be a lot friendlier than just throwing them away. If I am way off base, I fully expect to be corrected (with volume). My flame retardant suit is in place. Michael -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Phil Rosenthal Sent: Wednesday, October 15, 2003 4:47 PM To: John Palmer Cc: nanog@merit.edu Subject: Re: Pitfalls of annoucing /24s http://info.us.bb.verio.net/routing.html#PeerFilter That's how Verio does it, and I assume, that's how most people who filter by length do it as well. --Phil On Oct 15, 2003, at 4:40 PM, John Palmer wrote:

Good question.

You know there are thousands of legacy /24's out there that were allocated by IANA as /24's How can you aggregate them up if all you have is the

/24?

To those who filter out /24's - how is this done - just by the netmask

size?

----- Original Message ----- From: "Jean-Christophe Smith" <jsmith@vitalstream.com> To: <nanog@merit.edu> Sent: Wednesday, October 15, 2003 15:34 Subject: Pitfalls of annoucing /24s

...

In current practice would there be serious jeopardy of portions of

the

...

internet not being able to reach this address space due to bgp filters or other restrictions? What is the smallest acceptable block of IPs that

...

can be announced without adverse or unpredictable results? Verio would most likely be picking up these routes from us. I don't want to cause a religious debate, but I am interested in what the industry consensus is.

I'm just doing some research, any comments would be appreciated.

Thanks, Jean-Christophe Smith

--Phil Rosenthal ISPrime, Inc.