openstack，提示Invalid config option |dhcp_subnet

建立云主机的时候，提示没有找到 valid host。查看日志发现是 Invalid config option |dhcp_subnet_cidr|, value |None|.\n\n']。

觉得很奇怪啊，明明在nova.conf里面配置了相关的字段

## network ##
dhcp_subnet = true
dhcp_subnet_cidr = 1:192.168.138.0/24
dhcp_subnet_start =1:192.168.138.10

使用nova manage命令后发现

root@debian228:/data/log/nova# nova-manage network list
id       IPv4                  IPv6               start address      DNS1               DNS2               VlanID             project            uuid           
2        192.168.138.0/24      None               192.168.138.2      8.8.4.4            None               None               None               fa840d15-7c1d-4bd2-ade2-0bad1719b2fe

这个id竟然是2

以前一直不知道 dhcp前面那个 1：xxx中的1表示什么意思，现在才发现原来就是network的id。

出现这个问题是由于我一开始建立了一个固定ip段，发现错了，又删除了这个ip段，导致现在这个ip端的id为2！

在usr/lib/python2.7/dist-packages/nova/network/manager.py中，

 try:
            if network['cidr']:
                address = kwargs.get('address', None)
                if address:
                    address = self.db.fixed_ip_associate(context,
                                                         address,
                                                         instance_id,
                                                         network['id'])
                else:
                    if CONF.dhcp_subnet:
                        subnet_cidr = CONF.dhcp_subnet_cidr.get(
                                                    str(network['id']))
                        subnet_start = CONF.dhcp_subnet_start.get(
                                                    str(network['id']))
                        # NOTE(stanzgy): ensure the dhcp subnet configs are
                        # valid.
                        try:
                            netaddr.IPNetwork(subnet_cidr)
                        except Exception:
                            raise exception.InvalidConfig(
                                            key='dhcp_subnet_cidr',
                                            value=str(subnet_cidr))

也可以发现是根据这个id来查找network的