I am setting up multiple UML machines to simulate multiple machines communicating through a router using "http://read.cs.ucla.edu/click/"; . So, I need separate virtual interfaces for each UML so that the router can see several machines.
Actually, I figured out the problem of why my second UML machine is not able to talk to the world. It sends arp request for which there is no response. When the first UML machines runnning on tap2 asks for arp requests: [r...@host machine]# tcpdump -i tap2 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on tap2, link-type EN10MB (Ethernet), capture size 96 bytes 01:30:06.156300 arp who-has 192.168.1.3 tell 192.168.1.157 01:30:06.159457 arp reply 192.168.1.3 is-at 7e:6c:d7:2b:4b:c2 (oui Unknown) But, there is no reply when UML 2 asks : [r...@host machine]# tcpdump -i tap3 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on tap3, link-type EN10MB (Ethernet), capture size 96 bytes 01:30:47.696259 arp who-has 192.168.1.2 tell 192.168.1.221 01:30:48.687073 arp who-has 192.168.1.2 tell 192.168.1.221 01:30:49.687283 arp who-has 192.168.1.2 tell 192.168.1.221 01:30:50.699133 arp who-has 192.168.1.2 tell 192.168.1.221 01:30:51.699274 arp who-has 192.168.1.2 tell 192.168.1.221 Is there any reason why this should happen ? The commands that I used for setting up tap2 and tap3 are : tunctl -t tap2 ifconfig tap2 192.168.1.2 up echo 1 > /proc/sys/net/ipv4/conf/tap2/proxy_arp iptables -I FORWARD -o tap2 -j ACCEPT iptables -I FORWARD -i tap2 -j ACCEPT tunctl -t tap3 ifconfig tap3 192.168.1.3 up echo 1 > /proc/sys/net/ipv4/conf/tap3/proxy_arp iptables -I FORWARD -o tap3 -j ACCEPT iptables -I FORWARD -i tap3 -j ACCEPT route add -host 192.168.1.2 dev tap2 route add -host 192.168.1.3 dev tap3 arp -Ds 192.168.1.2 eth0 pub arp -Ds 192.168.1.3 eth0 pub echo 1 > /proc/sys/net/ipv4/ip_forward iptables -t nat -I POSTROUTING -o eth0 -j MASQUERADE echo 512 > /proc/sys/net/ipv4/neigh/default/gc_thresh1 echo 1024 > /proc/sys/net/ipv4/neigh/default/gc_thresh2 echo 2048 > /proc/sys/net/ipv4/neigh/default/gc_thresh3 echo 1 > /proc/sys/net/ipv4/conf/eth0/proxy_arp Any help is very much appreciated -Leo On Mon, Apr 26, 2010 at 1:57 AM, Rahul Gauba <rahul_ga...@yahoo.com> wrote: > Hi!, > > I think you can still work with a single tap device and keep it simple. > I generally run 4-5 UML on a single host and all of them are reachable from > other machines on the LAN. Assuming that my machine as a static IP > 10.121.32.231, I run multiple UML instances as: > ./linux-2.6.24-rc7 mem=1400M ubda=./Fedora_fs eth0=tuntap,,,10.121.32.231 > > When the UML comes UP, login to the UML instance, assign a static IP to > eth0 and add a default route on each UML instance. This should get all your > UMLs on the LAN. > > Thanks, > Rahul > > > > ------------------------------ > *From:* Leo Prasath <leo.pras...@gmail.com> > *To:* user-mode-linux-user@lists.sourceforge.net > *Sent:* Mon, April 26, 2010 10:04:40 AM > *Subject:* [uml-user] UML Networking setup > > Hi All, > > I am having trouble setting up networking with multiple UML instances on > the same machine. > > The host machine is on a subnet with IP 128.105.104.106. > > I am creating two UML instances and I want to make sure they both can > communicate with each other. > I do not want to use a bridge ( because I want all the packets to go > through the host machine so that I can play around with Click router > simulator ). > > I first tried creating two tap devices in the same subnet 192.168.0.0/24. > And I started two UML instances on each of these tap devices. > The first one could connect to outside world. But the second UML instance > had problems. > So, I tried with each of the tap devices on two different subnets like > below : > > > tap2 Link encap:Ethernet HWaddr 4E:E2:99:EE:A5:A1 > inet addr:192.168.0.2 Bcast:192.168.0.255 Mask:255.255.255.0 > inet6 addr: fe80::4ce2:99ff:feee:a5a1/64 Scope:Link > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > RX packets:524 errors:0 dropped:0 overruns:0 frame:0 > TX packets:407 errors:0 dropped:27 overruns:0 carrier:0 > collisions:0 txqueuelen:500 > RX bytes:55603 (54.2 KiB) TX bytes:62939 (61.4 KiB) > > tap3 Link encap:Ethernet HWaddr C6:04:42:8B:80:47 > inet addr:192.168.1.3 Bcast:192.168.1.255 Mask:255.255.255.0 > inet6 addr: fe80::c404:42ff:fe8b:8047/64 Scope:Link > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > RX packets:259 errors:0 dropped:0 overruns:0 frame:0 > TX packets:94 errors:0 dropped:27 overruns:0 carrier:0 > collisions:0 txqueuelen:500 > RX bytes:19790 (19.3 KiB) TX bytes:16796 (16.4 KiB) > > I have run the following commands for each of the tap devices : > > iptables -t nat -I POSTROUTING -o tap3 -j MASQUERADE > iptables -I FORWARD -o tap2 -j ACCEPT > iptables -I FORWARD -i tap2 -j ACCEPT > > I start my UML instances with the following commands: > > ./kernel64-2.6.33.2_64 ubda=CentOS5-AMD64-root_fs_64_2 > eth0=tuntap,tap3,fe:f0:00:00:00:03,192.168.1.3 con0=fd:0,fd:1 mem=256M > ./kernel64-2.6.33.2_64 ubda=CentOS5-AMD64-root_fs_64_1 > eth0=tuntap,tap2,fe:f0:00:00:00:03,192.168.0.2 con0=fd:0,fd:1 mem=256M > > Can someone give me some pointers on how to setup 2 or more UML instances > on the same host ? > > Thanks, > -Leo > >
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