From owner-freebsd-questions@FreeBSD.ORG Thu Mar 27 11:17:02 2003 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 33D9037B401 for ; Thu, 27 Mar 2003 11:17:02 -0800 (PST) Received: from dire.bris.ac.uk (dire.bris.ac.uk [137.222.10.60]) by mx1.FreeBSD.org (Postfix) with ESMTP id 322B543F85 for ; Thu, 27 Mar 2003 11:17:01 -0800 (PST) (envelope-from Jan.Grant@bristol.ac.uk) Received: from mail.ilrt.bris.ac.uk by dire.bris.ac.uk with SMTP-PRIV with ESMTP; Thu, 27 Mar 2003 19:16:54 +0000 Received: from cmjg (helo=localhost) by mail.ilrt.bris.ac.uk with local-esmtp (Exim 3.16 #1) id 18ycqY-0006vd-00; Thu, 27 Mar 2003 19:15:30 +0000 Date: Thu, 27 Mar 2003 19:15:30 +0000 (GMT) From: Jan Grant X-X-Sender: cmjg@mail.ilrt.bris.ac.uk To: James Earl In-Reply-To: <20030327185204.GA645@comp4.ici.net> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: Jan Grant X-Spam-Status: No, hits=-25.3 required=5.0 tests=EMAIL_ATTRIBUTION,IN_REP_TO,QUOTED_EMAIL_TEXT, REPLY_WITH_QUOTES,USER_AGENT_PINE autolearn=ham version=2.50 X-Spam-Level: X-Spam-Checker-Version: SpamAssassin 2.50 (1.173-2003-02-20-exp) cc: freebsd-questions Subject: Re: Reverse DNS and single IP address space X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 Mar 2003 19:17:03 -0000 On Thu, 27 Mar 2003, James Earl wrote: > On 2003.03.27 11:38 Victor Bondarenko wrote: > > On Thu, Mar 27, 2003 at 11:31:54AM -0700, James Earl wrote: > > [...] > > > Or, do I even need to worry about reverse DNS entries since my ISP > > > already has them setup? > > > > If your ISP has reverse DNS for your IP(s), there's really no point in > > you mapping them on your own. Your network might see whatever you've > > mapped, but the rest of the world will see what your ISP maps. > > I'm assuming if I can use nslookup [ip-address] to get my hostname, > that reverse DNS on the ISP is setup properly. Is this an okay > assumption? Not necessarily. Firstly, you want to know what nameserver you're getting that response from. Secondly, if the nameserver you're getting the response from belongs to the ISP, they might _think_ the reverse map is set up correctly, but upstream nameservers may disagree. You might want to pick a publicly-available nameserver and query it; alternatively, use nslookup or dig to follow the chain "by hand" from a root nameserver. The odds are you're ok, but checking by hand involves a little more work. You can do something like: > dig @a.root-servers.net 1.0.168.192.in-addr.arpa. ptr and you'll get a bit of the prefix and the next nameserver down to query (probably a list of them). Pick one and repeat the request until you get your ptr record back. That's what the rest of the world would do, effectively. Cheers, -- jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/ Tel +44(0)117 9287088 Fax +44 (0)117 9287112 http://ioctl.org/jan/ I shave with Occam's Razor.