Configure Network-Bridge

Hi,
I have some problems configuring my VMs to access them from my internal LAN.
my network: 192.168.9.0
my router and dhcp-server: 192.168.9.2
my server hosting VMs (proxmox): 192.168.9.1

in proxmox i have configured eth0 with 192.168.9.1, gateway 192.168.9.2, vmbr0 with ip 192.168.9.20. both are active.

after setting up a new VM i configured its network to be in bridged mode. via console i configured /etc/network/interfaces to:
auto eth0
address 192.168.9.21
netmask 255.255.255.0
gateway 192.168.9.2
dns-nameservers 192.168.9.2

when booting this vm, it receives an ip address 192.168.9.103. but i am not able to access the server from any pc on my network (only via console of proxmox).

can some one give me a hint? why is dhcp obviously active on this vm? what do i have to configure to be able to access my vm from any pc on my local network?

kind regards,
astrakid