From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: using same IP subnet on multiple interfaces (was: dual HCAs with upstream kernel) Date: Sun, 15 Aug 2010 10:59:46 -0600 Message-ID: <20100815165946.GA2861@obsidianresearch.com> References: <4C679C39.8060709@Voltaire.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4C679C39.8060709-hKgKHo2Ms0FWk0Htik3J/w@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Or Gerlitz Cc: "Hefty, Sean" , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Patrick McHardy List-Id: linux-rdma@vger.kernel.org On Sun, Aug 15, 2010 at 10:50:17AM +0300, Or Gerlitz wrote: > the echo requests go on the wire, the replies not, probably (...) > internally, Patrick? What all these settings do is let a socket that is bound to a device resolve the local host's address through ARP. The socket that is bound to a device will then use its device for sending, but other sockets not bound to devices will do route lookups and use the lo device. Do: ip route get 192.168.20.100 dev ib0 ip route get 192.168.20.1 src 192.168.20.100 To see the difference in each side. To really effect a full external loopback you need to have both sides bound to their respective devices. Note that binding to a device and binding to a source IP are not the same thing in Linux. In the RDMA CM case the listening side doesn't do any IP routing operations at all so a device bind isn't necessary. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html