proxmox 3.2 - internet down after a few seconds

i'm trying the latest proxmox and having problems with the network configuration
bridged network, below my configuration

# network interface settings
auto lo
iface lo inet loopback


iface eth0 inet manual


iface eth1 inet manual


auto vmbr0
iface vmbr0 inet static
address 10.100.100.251
netmask 255.255.255.0
gateway 10.100.100.2
bridge_ports eth0
bridge_stp off
bridge_fd 0


route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.100.100.0 0.0.0.0 255.255.255.0 U 0 0 0 vmbr0
0.0.0.0 10.100.100.2 0.0.0.0 UG 0 0 0 vmbr0


as soon as it boots up ping to 8.8.8.8 works for a few seconds that it stops working but ping to 10.100.100.2 my firewall/router is still responding.
service networking restart does the trick
again, a few seconds working ping to internet than once again, 100% packet lost.

anyone has some clue?

could it be my firewall?!? or something locally on proxmox that i missed?