Hi,

I'm trying to setup a GRE tunnel between an Ubuntu system and a UML (running on a different system). This is how the systems were configured:

1. UML

Boot arguments: ./vmlinux ubd0=guest3,uml-ext2-img con0=null con=fd:0,fd:1 umid=guest3 mem=32m eth0=tapng,,tap1 eth1=gre,,10.0.0.1,10.0.0.2,9 cgroup_disable=memory init=/etc/preinit

root@OpenWrt:/# ifconfig
eth0      Link encap:Ethernet  HWaddr 5A:86:C4:0D:19:F5
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:43 errors:0 dropped:22 overruns:0 frame:0
          TX packets:777 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:2321 (2.2 KiB)  TX bytes:312354 (305.0 KiB)
          Interrupt:5

eth1      Link encap:Ethernet  HWaddr 76:5A:7B:B7:D9:F6
          inet addr:192.168.252.1  Bcast:192.168.252.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:611 errors:0 dropped:611 overruns:0 frame:0
          TX packets:1 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:42518 (41.5 KiB)  TX bytes:402 (402.0 B)
          Interrupt:5

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

2. Ubuntu

This is the entry I added to /etc/network/interfaces:

auto gre1
iface gre1 inet static
        address 192.168.252.110
        netmask 255.255.255.252
        pre-up iptunnel add gre1 mode gre local 10.0.0.1 remote 10.0.0.2 ttl 255
        up ifconfig gre1 multicast
        pointtopoint 192.168.252.1
        post-down iptunnel del gre1

ubuntu# ifconfig

eth0      Link encap:Ethernet  HWaddr 78:e7:d1:c6:23:71
          inet addr:10.0.0.1  Bcast:10.78.49.255  Mask:255.255.255.0
          inet6 addr: fe80::7ae7:d1ff:fec6:2371/64 Scope:Link
          inet6 addr: 2001:220:abcd::20/64 Scope:Global
          inet6 addr: 2001:220:abcd:70::26/64 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3331 errors:0 dropped:284 overruns:0 frame:0
          TX packets:543 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1200307 (1.2 MB)  TX bytes:114051 (114.0 KB)
          Interrupt:17

gre1      Link encap:UNSPEC  HWaddr 0A-4E-31-4B-00-00-00-00-00-00-00-00-00-00-00-00
          inet addr:192.168.252.110  P-t-P:192.168.252.110  Mask:255.255.255.252
          inet6 addr: fe80::5efe:a4e:314b/64 Scope:Link
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1476  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:168 (168.0 B)

The ubuntu box is able to ping the IP 192.168.252.1, but strangely I don't see packets going out to 10.0.0.2. Also, the UML is not able to ping 192.168.252.110.

Is this configuration correct or is there something missing?

Thanks!