Nextserver

Nextserver is a term used in network booting to designate the address of the next server a client should contact to obtain boot files. It is commonly employed in conjunction with the Dynamic Host Configuration Protocol (DHCP) and the Preboot Execution Environment (PXE). The nextserver value points the client to the TFTP or boot server that hosts the initial boot image required to start an operating system installation or recovery process.

In DHCP and PXE workflows, the DHCP server may advertise the nextserver address in its replies so that the client knows where to fetch the boot file. The client then contact the specified server to download the boot image, such as a PXE bootstrap loader or a network-booted kernel. The nextserver value is typically paired with a boot file name, which tells the client exactly which file to retrieve from the boot server. If the nextserver is not provided, clients may fall back to using the DHCP server’s address or another configured default.

Configuration of nextserver varies by vendor and server role. In ISC DHCP, the next-server option can be set to a specific IP address. In Windows Server DHCP environments, option 66 is commonly used to specify the TFTP server name, while option 67 designates the boot file name. Effective use often requires coordinating the DHCP server, the TFTP server, and the path to the boot images, ensuring that the boot files are accessible and properly secured.

Security considerations include ensuring that only trusted boot servers are advertised, as directing clients to a compromised boot server can enable attacks at startup.