I am running RHEL 5 on virtualbox and I am unable to connect to the internet. Here are the results from ifconfig and route -n.

ifconfig
eth0 Link encap:Ethernet HWaddr 08:00:27:05:3F:F5
inet6 addr: fe80::a00:27ff:fe05:3ff5/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:110 errors:0 dropped:0 overruns:0 carrier:0
RX bytes:0 (0.0 b) TX bytes:8532 (8.3 KiB)

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/126 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:152 errors:0 dropped:0 overruns:0 frame:0
TX packets:152 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:12320 (12.0 KiB) TX bytes:12320 (12.0 Kib)

route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface

Are you running your Virtualbox virtual machine on a host that must pass a proxy server to access the internet ?

No, just a regular home router to my ISP.

Have you checked the virtualmachine's network options in Virtualbox ? Is it using NAT or something else (also the details settings) ?

Can your virtual machine ping your host ?

It seems you don't have IPv4 running at all,
- how is your eth0 configured (DHCP or static) ?

- do you have your network interface in Virtualbox Bridged (that's the way you will get to internet through your router) ?