Sae writes: | Have question about filtering policy on the natural class B address block. | Trying to use /21 or shorter for various places including international, | from the natural class B block, we have now. Do you see any problem on | announcing as /21 to the Internet? Yes. Give it back. Renumber into best-fit CIDR blocks from your provider(s) and/or IRR(s). Be a good citizen of the global routing tables, or be filtered. Sean.
You are going to have a very difficult time getting anything like global routability like this. /21s out of classical class B blocks are problematic. Negotiate the return of the /16 to an RIR, but requesting several /20s from current RIR issued space. You will be a good internet citizen and have superior routability. For classical class B space... /16 - almost certainly routable (nothing is absolute...) /17-/20 - Decent chance of routability /21-/24 - Will be filtered by some, but not all. /25-/32 - filtered by most - Daniel Golding -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of Sean M. Doran Sent: Friday, August 17, 2001 5:29 AM To: nanog@merit.edu; saeyul@netvein.com Subject: Re: Natural class B address Sae writes: | Have question about filtering policy on the natural class B address block. | Trying to use /21 or shorter for various places including international, | from the natural class B block, we have now. Do you see any problem on | announcing as /21 to the Internet? Yes. Give it back. Renumber into best-fit CIDR blocks from your provider(s) and/or IRR(s). Be a good citizen of the global routing tables, or be filtered. Sean. _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com
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