From owner-freebsd-net@FreeBSD.ORG Tue Oct 12 17:23:22 2010 Return-Path: Delivered-To: net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 36297106566C for ; Tue, 12 Oct 2010 17:23:22 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from asmtpout030.mac.com (asmtpout030.mac.com [17.148.16.105]) by mx1.freebsd.org (Postfix) with ESMTP id 1A1558FC12 for ; Tue, 12 Oct 2010 17:23:21 +0000 (UTC) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=us-ascii Received: from cswiger1.apple.com ([17.209.4.71]) by asmtp030.mac.com (Sun Java(tm) System Messaging Server 6.3-8.01 (built Dec 16 2008; 32bit)) with ESMTPSA id <0LA600HLIQU4CB90@asmtp030.mac.com> for net@freebsd.org; Tue, 12 Oct 2010 09:22:53 -0700 (PDT) X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 ipscore=0 suspectscore=5 phishscore=0 bulkscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx engine=6.0.2-1004200000 definitions=main-1010120076 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.2.15,1.0.148,0.0.0000 definitions=2010-10-12_10:2010-10-12, 2010-10-12, 1970-01-01 signatures=0 From: Chuck Swiger In-reply-to: Date: Tue, 12 Oct 2010 09:22:52 -0700 Message-id: <09A363D1-B678-42E2-A841-D762D631D07B@mac.com> References: <4CB2AF28.30309@rdtc.ru> <20101012152857.X2036@sola.nimnet.asn.au> <20101013010757.N2036@sola.nimnet.asn.au> To: Tom Evans X-Mailer: Apple Mail (2.1081) Cc: Ian Smith , net@freebsd.org Subject: Re: strange resolver behavour X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 12 Oct 2010 17:23:22 -0000 On Oct 12, 2010, at 8:30 AM, Tom Evans wrote: >> Taking the '5.3. Master file example' in RFC1035, what is the A response >> for 'ISI.EDU.' where the domain itself has no specific A RR? Would it >> be that of VENERA.ISI.EDU, or that of the first A listed, ie A.ISI.EDU? > > That domain has an MX record, so it wouldn't do either. When I do a > dig isi.edu, I just get a single A record, so I would assume an SMTP > server would attempt to deliver mail there. No, it would use the published MX records for the domain, and would first try delivering to vapor.isi.edu as the lowest precedence MX host listed: % dig -t mx isi.edu ; <<>> DiG 9.6.0-APPLE-P2 <<>> -t mx isi.edu ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 9344 ;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;isi.edu. IN MX ;; ANSWER SECTION: isi.edu. 706 IN MX 30 boreas.isi.edu. isi.edu. 706 IN MX 50 yin.isi.edu. isi.edu. 706 IN MX 10 vapor.isi.edu. isi.edu. 706 IN MX 20 nitro.isi.edu. Only if no MX records were found, would an MTA fall back to using the A record here: ;; QUESTION SECTION: ;isi.edu. IN A ;; ANSWER SECTION: isi.edu. 86123 IN A 128.9.176.20 Regards, -- -Chuck