Ubuntu – Internet not working after upgrade to Ubuntu 10.10

Try this:

1. Setup the virtualbox to use 2 adapters:
   • The first adapter is set to NAT (that will give you the internet connection).
   • The second adapter is set to host only.
2. Start the virtual machine and assign a static IP for the second adapter in Ubuntu (for instance 192.168.56.56). The host Windows will have 192.168.56.1 as IP for the internal network (VirtualBox Host-Only Network is the name in network connections in Windows). What this will give you is being able to access the apache server on ubuntu, from windows, by going to 192.168.56.56. Also, Ubuntu will have internet access, since the first adapter (set to NAT) will take care of that.
3. Now, to make the connection available both ways (accessing the windows host from the ubuntu guest) there's still one more step to be performed. Windows will automatically add the virtualbox host-only network to the list of public networks and that cannot be changed. This entails that the firewall will prevent proper access.
4. To overcome this and not make any security breaches in your setup:
   • go to the windows firewall section, in control panel,
   • click on advanced settings. In the page that pops up,
   • click on inbound rules (left column), then on new rule (right column). Chose custom rule, set the rule to allow all programs, and any protocol. For the scope, add in the first box (local IP addresses) 192.168.56.1, and in the second box (remote IP) 192.168.56.56. Click next, select allow the connection, next, check all profiles, next, give it a name and save.

That's it, now you have 2 way communication, with apache/any other service available as well as internet. The final step is to setup a share. Do not use the shared folders feature in virtualbox, it's quite buggy especially with windows 7 (and 64 bit). Instead use samba shares - fast and efficient.

Follow this link for how to set that up: https://wiki.ubuntu.com/MountWindowsSharesPermanently

Your DNAT rules need to be a bit more specific in order to work correctly. One way to proceed is to add a --destination (or -d) condition to each of them, e.g.

iptables -t nat -A PREROUTING -d $EXT_IP -p tcp --dport 80 -j DNAT \
    --to-destination 192.168.1.254

iptables -t nat -A PREROUTING -d $EXT_IP -p tcp --dport 22 -j DNAT \
    --to-destination 192.168.1.254

where $EXT_IP is your router's external (globally routable) IP address.

Caveat: If internal clients attempt to connect to the www or ssh services on 192.168.1.254 via the external (globally routable) IP address, then their connection attempts will fail (while connections directly to 192.168.1.254 would have succeeded).

To solve that, it is best to tell your internal clients to access the server via its internal IP address. Alternatively, you can configure a "hairpin NAT" by adding a couple more iptables rules, as follows:

iptables -t nat -A POSTROUTING -s 192.168.1.0/24 -d 192.168.1.254 -p tcp \
    --dport 80 -j SNAT --to-source $INT_IP

iptables -t nat -A POSTROUTING -s 192.168.1.0/24 -d 192.168.1.254 -p tcp \
    --dport 22 -j SNAT --to-source $INT_IP

where $INT_IP is the router's internal IP address (e.g. 192.168.1.1). With these rules, connections from internal clients to the external IP address will flow through the router. It is best to avoid doing hairpin NAT whenever possible, since it is a rather inefficient use of network and router system resources.