Qemu-kVM setup vm using 2 NIC's are not working

Discussion in 'Technical' started by muzi, Jan 13, 2011.

  1. muzi

    muzi New Member

    Hi Guys

    I am facing some strange problem as using 2 nic's on kvm child vm. Secondary interface eth1 is not working on vm but eth0 is working , i am using routing mode, here below details.

    Platform --> Fedora 13 (for both KVM host and child vm)

    Start VM using 2 nics support using below command.

    /usr/bin/qemu-kvm -M pc -m 256 -smp 1 -name myguest1 -uuid
    5dcb91e1 -nographic -monitor
    unix:/var/lib/libvirt/qemu/myguest1.monitor,server,nowait -boot c -drive
    file=/dev/vmdata/vm.root,if=ide,index=0,boot=on -drive
    file=/dev/vmdata/vm.var,if=ide,index=1 -drive
    file=/dev/vmdata/vm.swap,if=ide,index=3 -net
    nic,macaddr=52:54:00:ea:aa:fe,vlan=0,name=nic0 -net
    tap,ifname=tap3,script=/etc/KVM/vm-tap3.sh,vlan=0,name=tap3 -net
    nic,macaddr=52:54:00:a7:9b:c1,vlan=1,name=nic1 -net
    tap,ifname=tap30,script=/etc/KVM/vm-tap30.sh,vlan=1,name=tap30 -serial pty
    -parallel none -usb &

    VM is started and ifconfig shows both eth0 and eth1 in child vm.

    From KVM host, tap script using above add routes to desire ip. like

    ip route add dev tap3 (For eth0 on child VM guest)
    ip route add dev tap30 (For eth1 on child VM guest)

    Ip forwarding is enabled, and i ensure no traffic is blocked.

    Now when i ping eth0 ip ( from outside or inside KVM host mother its working. But when i ping eth1 ip ( from outside or even inside kvm mother its not working.

    After some diagonse, i conclude below.

    tcpdump on eth1 on child shows below.

    17:05:55.213100 ARP, Request who-has tell x.x.x.x, length 46
    17:05:56.213493 ARP, Request who-has tell x.x.x.xlength 46

    As on kvm host, arp -e shows below.

    [[email protected] ~]# arp -e
    Address HWtype HWaddress Flags Mask Iface
    x.x.x.x ether 52:54:00:56:40:56 C tap1
    x.x.x.x (incomplete) tap30

    As tap30 used by eth1 on child vm and tap1 used by eth0 on child vm. So its shows arp request not completed.

    Above setup is working f9 till FC-11, but i see from FC-12, libvirt drop process capabilities for interface ethernet, but above setup is still working f9 4 me using 1 int eth0 but eth1 is not working.

    Can you guys please suggest,

  2. muzi

    muzi New Member

    problem resolved successfully

    Problem has been resolved now after disabling rp_filter for desire interfaces :)

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