unable to add subnet for vm's

[h0nIg]

i tried to add the subnet to a hetzner root server (tried this: http://wiki.hetzner.de/index.php/Proxmox_VE and other tutorials) without success
no ping from host to guest and vice versa is possible. proxmox version 2.1-1

x.x.x.13 = main ip
y.y.y.120/29 = additional subnet

host (debian):
uname -a:

2.6.32-12-pve

/etc/network/interfaces

auto  eth0
iface eth0 inet static
  address     x.x.x.13
  broadcast   x.x.x.31
  netmask     255.255.255.255
  gateway     x.x.x.1

auto vmbr0
iface vmbr0 inet static
  address      x.x.x.13
  netmask      255.255.255.255
  broadcast    x.x.x.31
  bridge_ports none
  bridge_stp   off
  bridge_fd    0
  up route add -net y.y.y.120/29 dev vmbr0
  down route del -net y.y.y.120/29 dev vmbr0

sysctl config

net.ipv4.ip_forward=1
net.ipv4.conf.all.rp_filter=1
net.ipv4.icmp_echo_ignore_broadcasts=1
net.ipv6.conf.all.proxy_ndp=1

guest 1 (ubuntu 12.04)
uname -a:

3.2.0-23-generic

/etc/network/interfaces

auto eth0
iface eth0 inet static
  address y.y.y.121
  netmask 255.255.255.248
  broadcast x.x.x.31
  gateway x.x.x.13

a network restart on guest 1 will result in

$ service networking restart
stop: Unknown instance:
networking stop/waiting

ping of the host (inside guest)

$ ping x.x.x.13
connect: Network is unreachable

any ideas abount this problem?