Hi, 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 ! -- Philippe