Dear all, when debugging why PXE booting didn't work after switching from ISC-dhcp to freeradius I noticed, that the "next-server" in ISC is in freeradius taken from "DHCP-Server-IP-Address". This field "siaddr" in the DHCP Packets (not in the option area) ist used by the clients. A comment in raddb/sites-available/dhcp says: # The source IP for unicast packets is chosen from the first # one of the following items which returns a valid IP # address: # # src_ipaddr # ipaddr # reply:DHCP-Server-IP-Address # reply:DHCP-DHCP-Server-Identifier So I never thought that I need to use "DHCP-Server-IP-Address" for the TFTP server (which is not the same as the dhcp server at our site). The first usefull hint was https://github.com/nagios-plugins/nagios-plugins/blob/master/plugins-root/ch...: /* * RFC 2131 (2.) says: "DHCP clarifies the interpretation of the * 'siaddr' field as the address of the server to use in the next step * of the client's bootstrap process. A DHCP server may return its own * address in the 'siaddr' field, if the server is prepared to supply * the next bootstrap service (e.g., delivery of an operating system * executable image). A DHCP server always returns its own address in * the 'server identifier' option." So the setting of "siaddr" in freeradius for pxe booting to a different server seems to be not possible, if you need to set the DHCP-Server-IP-Address also dynamically in freeradius processing. Sorry if I misunderstand things - I'm not fluent in the RFC and PXE stuff in BIOS. Thanks a lot, greetings Hermann P.S: A quick check of v4 master seems to have a syntax change only in the raddb comment -- Administration/Zentrale Dienste, Interdiziplinaeres Zentrum fuer wissenschaftliches Rechnen der Universitaet Heidelberg IWR; INF 205; 69120 Heidelberg; Tel: (06221)54-14405 Fax: -14427 Email: Hermann.Lauer@iwr.uni-heidelberg.de