Xen guest – cannot get network connection beyond the host

I've just installed a XenServer 6.1. It came with a standard configuration, network 0 connected to NIC 0.

I created a VM but I can't reach any network beyond the host.

From the VM (172.18.32.20), I try to ping 172.18.32.254.

Trying to make it work, I brought the following changes to the host base configuration:

• xe-switch-network-backend bridge
• reboot

• edit sysctl.conf:

  net.ipv4.ip_forward = 1
  net.ipv4.icmp_echo_ignore_broadcasts = 1
  net.ipv4.conf.all.arp_filter = 1
  net.ipv4.conf.default.proxy_arp = 1
  

• run sysctl -p

• stop iptables /etc/init.d/iptables stop
• run iptables -A FORWARD -j ACCEPT

"Ifconfig -a" shows 4 interfaces: eth0, lo, vif12.0 (my VM) and xenbr0 (IP=172.18.32.10, netmask=255.255.255.0, gateway=178.18.32.254)

$ brctl show
bridge name   bridge id          STP enabled   interfaces
xenbr0        5000.042b21457249  no            eth0
                                               vif12.0

After all that, my VM still can ping 172.18.32.10 but not 172.18.32.254.

The host can ping it.

Can someone tell me how to proceed and if bridging is the right thing to do?