LXC on Debian 11 , Debian 10 in container will not configure routing from outside

When our config contains line
lxc.net.0.veth.ipv4.route = 81.48.43.192/28
the container will not start writing

lxc-start template_debian_buster 20210506102755.865 ERROR network - network.c:lxc_setup_ipv4_routes:130 - File exists - Failed to setup ipv4 route for network device with ifindex 28
lxc-start template_debian_buster 20210506102755.865 ERROR network - network.c:instantiate_veth:345 - Failed to setup ipv4 routes for network device “vethITd3t3”
lxc-start template_debian_buster 20210506102755.946 ERROR network - network.c:lxc_create_network_priv:3068 - File exists - Failed to create network device
lxc-start template_debian_buster 20210506102755.946 ERROR start - start.c:lxc_spawn:1786 - Failed to create the network
lxc-start template_debian_buster 20210506102755.946 ERROR lxccontainer - lxccontainer.c:wait_on_daemonized_start:859 - Received container state “ABORTING” instead of “RUNNING”
lxc-start template_debian_buster 20210506102755.946 ERROR lxc_start - tools/lxc_start.c:main:308 - The container failed to start
lxc-start template_debian_buster 20210506102755.946 ERROR lxc_start - tools/lxc_start.c:main:311 - To get more details, run the container in foreground mode
lxc-start template_debian_buster 20210506102755.946 ERROR lxc_start - tools/lxc_start.c:main:313 - Additional information can be obtained by setting the --logfile and --logpriority options
lxc-start template_debian_buster 20210506102755.947 ERROR start - start.c:__lxc_start:1999 - Failed to spawn container “template_debian_buster”

Is it possible do the routing routing inside container using lxc.net.0.script.up ? The sripts runs outside container, but when we try run something inside it hangs.
The networking configuration outside container on the host is better managable as all the virtuals have the same gateway and routing. If we do the same inside contoiner in the /etc/network/interfaces it works fine, but the gateway has to be mannualy changed when we move container to different machine.
LXC verion is 4.0.6

Our config.

Common configuration

lxc.include = /usr/share/lxc/config/debian.common.conf

lxc.rootfs.path = zfs:ovps/template_debian_buster

lxc.net.0.type = veth
lxc.net.0.link = vmbr0
lxc.net.0.flags = up
lxc.net.0.ipv4.address = 192.168.144.71/24
lxc.net.0.veth.ipv4.route = 81.48.43.192/28
lxc.include = /var/lib/lxc/default_gateway_to_incude

lxc.apparmor.profile = generated
lxc.apparmor.allow_nesting = 1

Container specific configuration

lxc.tty.max = 4
lxc.uts.name = template_debian_buster
lxc.arch = amd64
lxc.pty.max = 1024
lxc.start.auto = 1
lxc.cgroup.memory.limit_in_bytes = 1024M