OK, some more information!
Can somebody have a look on these configuration files and look for mistakes, please?
/system/library/lauchdaemons/bootps.plist:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Disabled</key>
<true/>
<key>Label</key>
<string>com.apple.bootpd</string>
<key>ProgramArguments</key>
<array>
<string>/usr/libexec/bootpd</string>
</array>
<key>inetdCompatibility</key>
<dict>
<key>Wait</key>
<true/>
</dict>
<key>Sockets</key>
<dict>
<key>Listeners</key>
<dict>
<key>SockServiceName</key>
<string>bootps</string>
<key>SockType</key>
<string>dgram</string>
<key>SockFamily</key>
<string>IPv4</string>
</dict>
</dict>
</dict>
</plist>
/etc/bootpd.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>NetBoot</key>
<dict/>
<key>Subnets</key>
<array>
<dict>
<key>allocate</key>
<true/>
<key>dhcp_domain_name</key>
<string>hlg.hh.schule.de</string>
<key>dhcp_domain_name_server</key>
<array>
<string>10.0.111.6</string>
<string>10.0.111.1</string>
</array>
<key>dhcp_domain_search</key>
<array>
<string>hlg.hh.schule.de</string>
</array>
<key>dhcp_router</key>
<string>10.0.111.1</string>
<key>lease_max</key>
<integer>3600</integer>
<key>name</key>
<string>Schulnetz</string>
<key>net_address</key>
<string>10.0.111.0</string>
<key>net_mask</key>
<string>255.255.255.0</string>
<key>net_range</key>
<array>
<string>10.0.111.52</string>
<string>10.0.111.200</string>
</array>
<key>selected_port_name</key>
<string>en0</string>
<key>uuid</key>
<string>3B40680D-C3D0-44F5-88D0-B142E283FDC0</string>
</dict>
</array>
<key>allow</key>
<array/>
<key>bootp_enabled</key>
<false/>
<key>deny</key>
<array/>
<key>detect_other_dhcp_server</key>
<false/>
<key>dhcp_enabled</key>
<array>
<string>en0</string>
</array>
<key>netboot_disabled</key>
<array>
<string>en0</string>
</array>
<key>old_netboot_enabled</key>
<false/>
<key>relay_enabled</key>
<false/>
<key>relay_ip_list</key>
<array/>
<key>timeServiceStarted</key>
<string>2016-05-14 04:59:11 +0000</string>
</dict>
</plist>
Also would be nice to know in which file the defined static-IP-adresses are stored and where I can find it.
Thank you for your assistance,
Peter.