How to route all traffic from vm to vm on OS X

Challenge: to get one Debian VM (Virtualbox) to route all its traffic through another Debian VM (Paralles), both hosted under OS X 10.11.5. I've tried for days, I hope you can help here.

Schema:

vm1 (Virtualbox) ---> ( OS X ) --> vm2 (Parallels) --> inteet

This is what I have:

VM1 (the “client”):

• Interface eth1 setup with Host-only Network under Virtualbox, gets ip address 192.168.56.103 with netmask 255.255.255.0

VM2 (the “router”):

• Wifi card attached directly to the VM, interface wlan0 with ip 10.251.26.168, connected to inteet. wlan0 will be my outgoing interface.

• Interface eth0 setup as host-only under Parallels, gets ip address 10.37.129.6 with netmask 255.255.255.0.

On the host:

• VM1 is connected to interface vboxnet0 with ip 192.168.56.1 VM2 is connected to interface vnic1 with ip 10.37.129.2

With this setup pinging the host from each VM and viceversa works perfectly well (on their respective networks).

What I’ve done so far:

Under the host OS X systems I enable ip forwarding and bridge both virtual interfaces together:

bash-3.2# sysctl -w net.inet.ip.forwarding=1
net.inet.ip.forwarding: 1 -> 1
bash-3.2# ifconfig bridge0 create
bash-3.2# ifconfig vnic1 down
bash-3.2# ifconfig vboxnet0 down
bash-3.2# ifconfig bridge0 up addm vnic1 addm vboxnet0
bash-3.2# ifconfig vnic1 up
bash-3.2# ifconfig vboxnet0 up
bash-3.2# ifconfig bridge0
bridge0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
    options=3<RXCSUM,TXCSUM>
    ether ba:e8:56:14:5f:00 
    Configuration:
        id 0:0:0:0:0:0 priority 0 hellotime 0 fwddelay 0
        maxage 0 holdcnt 0 proto stp maxaddr 100 timeout 1200
        root id 0:0:0:0:0:0 priority 0 ifcost 0 port 0
        ipfilter disabled flags 0x2
    member: vnic1 flags=3<LEARNING,DISCOVER>
            ifmaxaddr 0 port 14 priority 0 path cost 0
    member: vboxnet0 flags=3<LEARNING,DISCOVER>
            ifmaxaddr 0 port 12 priority 0 path cost 0
    Address cache:
    media: autoselect
    status: active
bash-3.2# ifconfig vnic1
vnic1: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500
    options=3<RXCSUM,TXCSUM>
    ether 00:1c:42:00:00:09 
    inet 10.37.129.2 netmask 0xffffff00 broadcast 10.37.129.255
    media: autoselect
    status: active
bash-3.2# ifconfig vboxnet0
vboxnet0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500
    ether 0a:00:27:00:00:00 
    inet 192.168.56.1 netmask 0xffffff00 broadcast 192.168.56.255

On VM1 (“client”) I add default gateway:

root@vm1:~# ip route del 0/0
root@vm1:~# route -n
Keel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
  192.168.56.0    0.0.0.0         255.255.255.0   U     100    0        0 eth1
root@vm1:~# route add default gw 192.168.56.1
root@vm1:~# route -n
Keel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
  0.0.0.0         192.168.56.1    0.0.0.0         UG    0      0        0 eth1
  192.168.56.0    0.0.0.0         255.255.255.0   U     100    0        0 eth1

On VM2 (“router”) I enable ip forwarding and setup nat:

root@vm2:~# sysctl -w net.ipv4.ip_forward = 1
root@vm2:~# iptables -t nat -A POSTROUTING --out-interface wlan0 -j MASQUERADE  
root@vm2:~# iptables -A FORWARD --in-interface eth0 -j ACCEPT

Now, after all this I can ping from VM1 to 192.168.56.1 and 10.37.129.2 (host-side IPs for the virtual network adapters vboxnet0 and vnic1 respectively) but I can’t ping 10.37.129.6. I have also failed so far to access the inteet from VM1 through VM2 (from VM1 ping 8.8.8.8):

root@vm1:~# ping -c 1 192.168.56.1
PING 192.168.56.1 (192.168.56.1) 56(84) bytes of data.
64 bytes from 192.168.56.1: icmp_seq=1 ttl=64 time=1.54 ms

--- 192.168.56.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.543/1.543/1.543/0.000 ms

root@vm1:~# ping -c 1 10.37.129.2

PING 10.37.129.2 (10.37.129.2) 56(84) bytes of data.
64 bytes from 10.37.129.2: icmp_seq=1 ttl=64 time=0.208 ms

--- 10.37.129.2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.208/0.208/0.208/0.000 ms

root@vm1:~# ping -c 1 10.37.129.6
PING 10.37.129.6 (10.37.129.6) 56(84) bytes of data.

--- 10.37.129.6 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

root@vm1:~# ping -c 1 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.

--- 8.8.8.8 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

So I can't get VM1 to route all its traffic through VM2... what am I missing??

In case it helps troubleshooting, I launched wireshark on vm2 ("the router") listening to all interfaces. When I ping 10.37.129.6 from vm1, I see the ARP requests "who was 10.37.129.6 Tell 10.37.129.2", the corresponding ARP reply and the subsequent ICMP originating from vm1's ip (192.168.56.101) so the OS X bridge must be working. But I don't seem to get the ping response back to vm1 neither I see it on wireshark. And when I ping 8.8.8.8 from vm1 I don't see anything in vm2's wireshark session.

Thanks a lot for your help.

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