From owner-freebsd-net Tue Jul 3 12:12: 7 2001 Delivered-To: freebsd-net@freebsd.org Received: from herbelot.dyndns.org (d020.dhcp212-27.cybercable.fr [212.198.27.20]) by hub.freebsd.org (Postfix) with ESMTP id 3C19B37B406 for ; Tue, 3 Jul 2001 12:12:03 -0700 (PDT) (envelope-from thierry@herbelot.com) Received: from herbelot.com (multi.herbelot.nom [192.168.1.2]) by herbelot.dyndns.org (8.9.3/8.9.3) with ESMTP id VAA05377; Tue, 3 Jul 2001 21:10:07 +0200 (CEST) (envelope-from thierry@herbelot.com) Message-ID: <3B4218DD.A1DAAB51@herbelot.com> Date: Tue, 03 Jul 2001 21:11:25 +0200 From: Thierry Herbelot X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.2.12 i386) X-Accept-Language: en MIME-Version: 1.0 To: Juan Fco Rodriguez Hervella Cc: Lista Subject: Re: How to send packets to another interface on the same machine References: <3B420C63.41C48FBB@it.uc3m.es> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org Juan Fco Rodriguez Hervella wrote: > > Dear all: > > I have the following problem: I would like to send an IPv6 packet using > a given > interface, to the address that corresponds to another interface of the > same machine. > > This, that seems a bit akward, it would be interesting for obtaining > accurate > packet latency results to test other systems that could be placed > between the > two interfaces (routers, etc.). Since the sending and the receiving > process share > the same physical clock, microsecond precision could be obtained in the > measures. > > The problem is that FreeBSD recognises that the destination address is > in the same > machine, and routes directly through the loopback interface, without > sending actually > the packets through the wire. > > Anyone knows a trick to do this? I have recently built a similar test bench, but for latency accuracies in the order of 1 ms (instead of some usecs), using ntp to synchronize the machines. This way, I could measure the the travelling time of packets down to a 1 ms accuracy (from one PC to another, both being synchronized to the same NTP master server) HtH -- Thierry Herbelot To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message