The project I am working on involves using multiple distributions of Linux, and since I don't want to multi-boot I am using VirtualBox to develop specific things for each distro. I am running Windows 7 Ultimate 64 bit on the host machine.
After I had installed CentOS 6.2 in a virtual machine I ran into trouble with connecting to the internet. I tried using NAT, bridged, and host-only options in the network settings for the VM and still no such luck. After some googling and banging my head on my keyboard trying to find a solution I had come up with nothing that had worked. I eventually came across a post in the Debian forums that gave a couple of commands that I punched into the shell, more specifically the route command.
The output of the route command was as follows:
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 1003 0 0 eth0
... or something to that extent.
The issue was that I was behind a router and it wasn't reaching external networks. I was able to ping other VMs and my host machine and from both the guest and the host, but not able to ping google.ca. I would get a message telling me "network is unreachable".
The problem was solved when I changed the configuration a little bit in /etc/sysconfig/network-scripts/ifcfg-eth0. I appended the following lines to the file. I might also note here that when you configure your ifcfg file to work behind a router, the IP that you choose to use (I use a static internal IP for consistency, and it might be wise if you will be using them as virtual hosts) needs to be in the same network as your router. My router gateway is at 192.168.0.1 and this VM is using the static IP 192.168.0.19.
The entire file in it's working state is:
After editing the fie and running /etc/init.d/network restart I was able to ping google and update/install things through yum.
That's what worked for me, if you've run into the same problem and were able to solve it in a different way please do let me know how you were able to solve it.
Upon setting up yet another VM and running into this same problem using Bridged Networking in Virtualbox, I was able to ping local machines, but not external machines on the internet or domain names.
To fix this issue and be able to resolve domains, I added this line to /etc/resolv.conf:
After this I was able to resolve domains. There's probably another fix for that to do with the settings I configured previously, perhaps not. That's what worked for me and for those of you who don't know, 126.96.36.199 is one of the IPs for google's public DNS servers.