From mboxrd@z Thu Jan 1 00:00:00 1970 From: Antonio Pinizzotto Date: Fri, 01 Jul 2005 18:37:44 +0000 Subject: Re: [LARTC] linux bridging problem: how to emulate 2 separate Message-Id: <42C58D78.9010701@iit.cnr.it> List-Id: References: <42C513EC.6030505@iit.cnr.it> In-Reply-To: <42C513EC.6030505@iit.cnr.it> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lartc@vger.kernel.org Stephen Hemminger wrote: > On Fri, 01 Jul 2005 11:59:08 +0200 > Antonio Pinizzotto wrote: > > >>Hi all. >> >>I would need to use a single physical interface on a Linux box to manage >>two different IP addresses (belonging to two separate logical subnets) >>with two different MAC address. (I need to emulate te presence of two >>separate physical interfaceses for a PC on the same LAN, at layer 2 and >>layer 3). >> >>Is it possible to use the linux ethernet bridging code and two tap >>interfaces for this purpose? >> >> >>Here is a picture of what I need to do. >> >> >> LAN__________________________________ >> | >> | eth0 (no IP) >> ________|________ >> | | >> | br0 | >> | (no IP) | >> |_________________| >> tap0 | | tap1 >>192.168.40.1/24 | | 192.168.30.1/24 >> MAC_0 | | MAC_1 >> __|________|__ >> | | >> | PC | >> | | >> |______________| >> >> >>I would need this picture to be equivalent to this one: >> >> >> LAN__________________________________ >> eth0 | | eth1 >>192.168.40.1/24 | | 192.168.30.1/24 >> MAC_0 | | MAC_1 >> __|________|__ >> | | >> | PC | >> | | >> |______________| >> >> >>I tried but it doens't work. I don't know if it's not contemplate or if >>I did a wrong configuration. >>For example, on tap0, using tcpdump, I see all the L2 broadcast frames >>going on the LAN; but on the counters of "ifconfig tap0" all of them are >>considered dropped. No packet is counted as transmitted or received, >>also if I try to ping from or to tap0. >>The tap interface starts to transmit/receive pachets only if it is >>connected to some process like qemu or openvpn. >>Maybe, it is not possibile for tap interface to be used directly by the >>linux os? >> > > > > Stop abusing bridging. People keep trying these wacky multiple > network things and they won't work. Bridging really can't handle anything > with multiple interfaces that could possibly create a forwarding loop. > > > Dear Stephen, probably my pictures or descriptions were not so clear. I don't want abuse bridging. As you can see in the second picture (of the previous e-mail) I just would like to replicate the real topology (in which there are not loops because each physical interface has its own subnet) using software interfaces, taps. Moreover in the second picture no bridging is enabled on the PC. It is just an experiment to understand how the various software pieces works togheter. Below I tried to draw a clearer picture. The first one is what I would like to get. The second one is what I have. LAN______________________________________________ | | eth0 (no IP) _____________________|________________________ | | Linux Box (PC)| | ________|________ | | | | | | | br0 | | | | (no IP) | | | |_________________| | | tap0 | | tap1 | | 192.168.40.1/24 | | 192.168.30.1/24 | | MAC_0 | | MAC_1 | | ___|________|____ | | | | | | | OS TCP-IP stack | | | | | | | |_________________| | | | | | | | | | | | | | | Processes | | | | | |______________________________________________| I would need the first picture to be equivalent to the next one: LAN_____________________________________________ eth0 | | eth1 192.168.40.1/24 | | 192.168.30.1/24 MAC_0 | | MAC_1 _________________|________|___________________ | | | Linux Box (PC)| | ___|________|____ | | | | | | | OS TCP-IP stack | | | | | | | |_________________| | | | | | | | | | | | | | | Processes | | | | | |______________________________________________| Bye Antonio _______________________________________________ LARTC mailing list LARTC@mailman.ds9a.nl http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc