A method for obtaining a local domain name, comprising: receiving, by a DHCP server, a Dynamic Host Configuration Protocol, DHCP, request of a User Equipment, UE, wherein the DHCP request carries an option for indicating returning a domain name of a local domain where the UE is located; and obtaining, by the DHCP server according to the DHCP request, the domain name of the local domain where the UE is located, and carrying, in a DHCP reply message to be returned to the UE, the domain name of the local domain where the UE is located; wherein the domain name of the local domain is for use in re-authentication of the UE during a handover; wherein the obtaining the domain name of the local domain where the UE is located comprises: obtaining, by the DHCP server, the domain name of the local domain where the UE is located from the DHCP request forwarded by a second server, wherein the DHCP request forwarded by the second server has been inserted with the domain name of the local domain where the UE is located, and the domain name of the local domain where the UE is located is obtained by the second server from a third server; wherein the second server is a Network Access Server, NAS, a DHCP relay, or a DHCP agent; and the third server is an Extensible Authentication Protocol, EAP, server, an Authentication, Authorization and Accounting, AAA, server with an EAP Re-authentication Protocol, ERP, function, or an AAA server with an EAP function. receiving, by a DHCP server, a Dynamic Host Configuration Protocol, DHCP, request of a User Equipment, UE, wherein the DHCP request carries an option for indicating returning a domain name of a local domain where the UE is located; and obtaining, by the DHCP server according to the DHCP request, the domain name of the local domain where the UE is located, and carrying, in a DHCP reply message to be returned to the UE, the domain name of the local domain where the UE is located; wherein the domain name of the local domain is for use in re-authentication of the UE during a handover; wherein the obtaining the domain name of the local domain where the UE is located comprises: obtaining, by the DHCP server, the domain name of the local domain where the UE is located from the DHCP request forwarded by a second server, wherein the DHCP request forwarded by the second server has been inserted with the domain name of the local domain where the UE is located, and the domain name of the local domain where the UE is located is obtained by the second server from a third server; wherein the second server is a Network Access Server, NAS, a DHCP relay, or a DHCP agent; and the third server is an Extensible Authentication Protocol, EAP, server, an Authentication, Authorization and Accounting, AAA, server with an EAP Re-authentication Protocol, ERP, function, or an AAA server with an EAP function. obtaining, by the DHCP server, the domain name of the local domain where the UE is located from the DHCP request forwarded by a second server, wherein the DHCP request forwarded by the second server has been inserted with the domain name of the local domain where the UE is located, and the domain name of the local domain where the UE is located is obtained by the second server from a third server; wherein the second server is a Network Access Server, NAS, a DHCP relay, or a DHCP agent; and the third server is an Extensible Authentication Protocol, EAP, server, an Authentication, Authorization and Accounting, AAA, server with an EAP Re-authentication Protocol, ERP, function, or an AAA server with an EAP function.