Maybe if you describe your issue better it would help but to start;
IPCONFIG IPCONFIG /all Display full configuration information. IPCONFIG /release [adapter] Release the IP address for the specified adapter. IPCONFIG /renew [adapter] Renew the IP address for the specified adapter. IPCONFIG /flushdns Purge the DNS Resolver cache. IPCONFIG /registerdns Refresh all DHCP leases and re-register DNS names. IPCONFIG /displaydns Display the contents of the DNS Resolver Cache. IPCONFIG /showclassid adapter Display all the DHCP class IDs allowed for adapter. IPCONFIG /setclassid adapter [classid] Modify the dhcp class id.