my $opts = PVE::Network::SDN::SubnetPlugin->check_config($id, $param, 0, 1);
$cfg->{ids}->{$id} = $opts;
+ raise_param_exc({ ipam => "you can't change ipam"}) if $opts->{ipam} && $scfg->{ipam} && $opts->{ipam} ne $scfg->{ipam};
+
PVE::Network::SDN::SubnetPlugin->on_update_hook($id, $opts, $scfg);
PVE::Network::SDN::Subnets::write_config($cfg);