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I am trying to set up two virtual networks(different subnets) to test site to site VPN in my Laptop. My host OS is Debian Wheezy and i am using Virtual box to virtualise my setup. I have two aliased private IP addresses on my host NIC along with a public IP address assigned from ISP provider. Below is my interface file.

/etc/network/interfaces

 # The loopback network interface
 auto lo
 iface lo inet loopback

 # The primary network interface
 allow-hotplug eth0
 iface eth0 inet dhcp

 auto eth0:1
 iface eth0:1 inet static
       address 192.168.1.1
       netmask 255.255.255.0

 auto eth0:2
 iface eth0:2 inet static
       address 192.168.2.1
       netmask 255.255.255.0

Output of command "ip a"(only the relevant parts)

 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
   link/ether 00:1b:38:99:c3:22 brd ff:ff:ff:ff:ff:ff
   inet 192.168.1.1/24 brd 192.168.1.255 scope global eth0:1
   inet 192.168.2.1/24 brd 192.168.2.255 scope global eth0:2
   inet 10.26.136.50/19 brd 10.26.159.255 scope global eth0
   inet6 fe80::21b:38ff:fe99:c322/64 scope link 
   valid_lft forever preferred_lft forever

Output of command "ip r"

default via 10.26.128.1 dev eth0 
10.26.128.0/19 dev eth0  proto kernel  scope link  src 10.26.136.50 
192.168.1.0/24 dev eth0  proto kernel  scope link  src 192.168.1.1 
192.168.2.0/24 dev eth0  proto kernel  scope link  src 192.168.2.1 
192.168.56.0/24 dev vboxnet0  proto kernel  scope link  src 192.168.56.1 
192.168.57.0/24 dev vboxnet1  proto kernel  scope link  src 192.168.57.1 
192.168.58.0/24 dev vboxnet2  proto kernel  scope link  src 192.168.58.1 

Now i have two VM's bridged to eth0 of host. VM Ip address details.

VM1 --- IP Address --> 192.168.1.10
VM2 --- IP Address --> 192.168.2.10

I can ping both the VM's from the host. Even i can access internet from both the VM's as i have a iptables MASQUERADE rule and ip forwarding enabled on the host.

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

sandy@sdebby:~$ sudo iptables -t nat -nvL POSTROUTING
Chain POSTROUTING (policy ACCEPT 47 packets, 2928 bytes)
pkts bytes target     prot opt in     out     source               destination         
1629  103K MASQUERADE  all  --  *      eth0    0.0.0.0/0            0.0.0.0/0 

sandy@sdebby:~$ sudo sysctl -p
net.ipv4.ip_forward = 1

But i can't ping one VM from the other and vice versa. All firewall rules are disabled on the VM's. When i do a tcpdump on the outer interface of the VM, i can see its receiving only icmp echo requests but not replying back. Below is the tcpdump output.

Tcpdump on VM1(192.168.1.10) while pinging from VM2(192.168.2.10)

[Expert@fw1-gw1]# tcpdump -ni eth0 host 192.168.2.10
tcpdump: listening on eth0
12:13:29.435073 192.168.2.10 > 192.168.1.10: icmp: echo request (DF)
12:13:30.461966 192.168.2.10 > 192.168.1.10: icmp: echo request (DF)
12:13:31.511685 192.168.2.10 > 192.168.1.10: icmp: echo request (DF)

Tcpdump on VM2(192.168.2.10) while pinging from VM1(192.168.1.10)

[Expert@fw1-gw2]# tcpdump -ni eth0 host 192.168.1.10
tcpdump: listening on eth0
12:15:55.228300 192.168.1.10 > 192.168.2.10: icmp: echo request (DF)
12:15:56.270639 192.168.1.10 > 192.168.2.10: icmp: echo request (DF)
12:15:57.295431 192.168.1.10 > 192.168.2.10: icmp: echo request (DF)

I have checked each VM can reach till the gateway of the other VM but not beyond that. So, i am suspecting that my routes are not working although they seems to be proper to me.

Do you see anything that i am missing? Any help will be highly appreciated.

Otherwise i will have to change my setup to keep both the VM's in same network, and i will be very unhappy with that.

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