North American Network Operators Group

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

RE: Natural class B address

  • From: Daniel Golding
  • Date: Fri Aug 17 17:52:13 2001

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: [email protected] [mailto:[email protected]]On Behalf Of
Sean M. Doran
Sent: Friday, August 17, 2001 5:29 AM
To: [email protected]; [email protected]
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.


Do You Yahoo!?
Get your free address at