proxmox ip change venet not working for VE's

I was trying to change an existing server ip (moving it into another subnet) and all seemed to work (after a restart) except output internet connectivity for the VE's


# Original network interface settings (that work)auto lo
iface lo inet loopback


iface eth0 inet manual


iface eth1 inet manual


iface eth2 inet manual


iface eth3 inet manual


auto vmbr0
iface vmbr0 inet static
address 192.168.20.51
gateway 192.168.20.254
netmask 255.255.252.0
bridge_ports eth0
bridge_stp off
bridge_fd 0


# Original network interface settings (that dont work)auto lo
iface lo inet loopback


iface eth0 inet manual


iface eth1 inet manual


iface eth2 inet manual


iface eth3 inet manual


auto vmbr0
iface vmbr0 inet static
address 192.168.21.51 # <---
gateway 192.168.20.254
netmask 255.255.252.0
bridge_ports eth0
bridge_stp off
bridge_fd 0


The thing is that I am able to ping internal network (ie 192.168.20.2) but not external network (8.8.8.8)

I don't think that its network issue since this configuration work just fine on other machine (both physical and KVM based machines on this proxmox instance) I suspect that it related somehow to internal proxmox routing setting but couldn't find any mention of this

Thanks