[CentOS] CentOS 5.6 x86_64 hosting unreachable Virtualbox 4.0.6 bridged guests

Tue Apr 26 08:28:40 UTC 2011
Philippe <lists at lrnx.ath.cx>


On a box running CentOS 5.6 x86_64 and Virtualbox 4.0.6, I have 
configured 2 guests (WinXP x86 + CentOS 5.6 x86_64) in bridged mode.
The hosting box and the two guests are dhcp enabled. The hosting box 
get its address normally, but the 2 hosted systems fail to get theirs.
The dhcp server log tells : DHCPDISCOVER from 08:00:xx:xx:xx:xx via 
em0: network xx.xx/16: no free leases.
When changing from dhcp to static ip in the CentOS guest, 'service 
network restart' does not report any errors, but the guest keeps 
unreachable from the outside : pinging the guest works some times, but 
trying to reach the guest with ssh, http, or ftp always fail, with or 
whitout iptables enabled on the host and/or the guests.

Please note that:
- Kernel and softwares on the hosting CentOS are up-to-date, the box 
has an Intel Corporation 82567LM-3 Gigabit Network Connection (rev 02) 
NIC, does not have an Intel VT compliant CPU (Pentium E5700), but 
VT/AMD-V enabled in bios.
- The host is not configured in bridged mode (does not have a br 
interface configured), Oracle telling that bridged mode on the host is 
not required to run Virtualbox guests in bridged mode.
- The 2 guests work perfectly in NAT mode, but this mode is not an 
option for me.
- The same 2 guests work perfectly in bridged mode on another same 
hosting box running Fedora 14.

Is anyone experimenting the same difficulties with Virtualbox on CentOS 
5.6 ? I don't know where to search to solve this problem.
Thanks for your help !