dhcpd 服务启动报错

报错信息：

Jun 22 14:57:59 localhost systemd: Starting DHCPv4 Server Daemon...
Jun 22 14:57:59 localhost dhcpd: Internet Systems Consortium DHCP Server 4.2.5
Jun 22 14:57:59 localhost dhcpd: Copyright 2004-2013 Internet Systems Consortium.
Jun 22 14:57:59 localhost dhcpd: All rights reserved.
Jun 22 14:57:59 localhost dhcpd: For info, please visit https://www.isc.org/software/dhcp/
Jun 22 14:57:59 localhost dhcpd: Not searching LDAP since ldap-server, ldap-port and ldap-base-dn were not specified in the config file
Jun 22 14:57:59 localhost dhcpd: Wrote 0 leases to leases file.
Jun 22 14:57:59 localhost dhcpd: 
Jun 22 14:57:59 localhost dhcpd: No subnet declaration for em2 (no IPv4 addresses).
Jun 22 14:57:59 localhost dhcpd: ** Ignoring requests on em2.  If this is not what
Jun 22 14:57:59 localhost dhcpd:   you want, please write a subnet declaration
Jun 22 14:57:59 localhost dhcpd:   in your dhcpd.conf file for the network segment
Jun 22 14:57:59 localhost dhcpd:   to which interface em2 is attached. **
Jun 22 14:57:59 localhost dhcpd: 
Jun 22 14:57:59 localhost systemd: dhcpd.service: main process exited, code=exited, status=1/FAILURE
Jun 22 14:57:59 localhost dhcpd: 
Jun 22 14:57:59 localhost systemd: Failed to start DHCPv4 Server Daemon.
Jun 22 14:57:59 localhost dhcpd: No subnet declaration for em1 (192.168.1.205).
Jun 22 14:57:59 localhost systemd: Unit dhcpd.service entered failed state.
Jun 22 14:57:59 localhost dhcpd: ** Ignoring requests on em1.  If this is not what
Jun 22 14:57:59 localhost systemd: dhcpd.service failed.
Jun 22 14:57:59 localhost dhcpd:   you want, please write a subnet declaration
Jun 22 14:57:59 localhost dhcpd:   in your dhcpd.conf file for the network segment
Jun 22 14:57:59 localhost dhcpd:   to which interface em1 is attached. **
Jun 22 14:57:59 localhost dhcpd: 
Jun 22 14:57:59 localhost dhcpd: 
Jun 22 14:57:59 localhost dhcpd: Not configured to listen on any interfaces!
Jun 22 14:57:59 localhost dhcpd: 
Jun 22 14:57:59 localhost dhcpd: This version of ISC DHCP is based on the release available
Jun 22 14:57:59 localhost dhcpd: on ftp.isc.org.  Features have been added and other changes
Jun 22 14:57:59 localhost dhcpd: have been made to the base software release in order to make
Jun 22 14:57:59 localhost dhcpd: it work better with this distribution.
Jun 22 14:57:59 localhost dhcpd: 
Jun 22 14:57:59 localhost dhcpd: Please report for this software via the CentOS Bugs Database:
Jun 22 14:57:59 localhost dhcpd:    http://bugs.centos.org/
Jun 22 14:57:59 localhost dhcpd: 

原因： 报错是由于dhcpd服务与服务器的网卡不在同一网段；配置服务器网卡后没有启动network，ip配置没有生效，导致dhcpd重启失败。