The system will automatically obtain IP solution occurring after breaking into a fixed IP network

This is because the router's LAN settings, check the DHCP (enable DHCP). Computer access is automatically assigned an IP address. Neither set a fixed IP address. 
DHCP (Dynamic Host Configuration Protocol, Dynamic Host Configuration Protocol) is a network protocol LAN, using the UDP protocol works, there are two main purposes: to automatically assign IP addresses to the internal network or Internet service provider to the user or an internal network administrator as a means for central management of all computers, are described in detail in RFC 2131. 
DHCP has three ports, and wherein UDP67 UDP68 normal DHCP service ports, respectively, as the DHCP Server and DHCP Client service port; 546 ports for DHCPv6 Client, and not for the DHCPv4, failover for the DHCP service, which is required special open service, DHCP failover is used to make "hot standby" in.