Problem solved. With this info:
http://help.ovh.co.uk/BridgeClient
Tested with a full KVM Centos.
I did set it up like:
/etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
USERCTL=no
IPV6INIT=no
PEERDNS=yes
TYPE=Ethernet
NETMASK=255.255.255.248 (Ripe FO IP mask)
IPADDR=IP Failover (Ripe FO)
GATEWAY=Dedicated Server IP but end in .254
ARP=yes
HWADDR=Your Virtual Mac Address
And manual tested the routing by using enter commands in remote ssh
session:
route add Dedicated Server IP but end in .254 dev eth0
route add default gw Dedicated Server IP but end in .254
On the Proxmox host i also did use:
ip route add YOUR_IP_FAILOVER dev vmbr1
Now all ok. I did not set a mac adres in the manager. It works like this in my case. Hope this info can help others.