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Network Portable Outlets for DHCP Service Users

Jean-Michel Jouanigot , IT/CS


Change of IP addresses on Network Portable Outlets.

In order to improve the quality of the DHCP service on the structured cabling portable outlets, and increase the number of addresses we can provide to the DHCP users, the setup of all Portable Outlets is progressively being changed.

The only visible impact for laptops (portable PCs and MACs) making use of DHCP on portable outlets is that the dynamically allocated addresses will become of the form 128.141.x.x instead of 137.138.x.x. (Some parts of the old 128.141 network are recycled for addressing with DHCP). Your system parameters will automatically be set to the correct values (default gateway, etc.), and you should not alter them in any way. Any optional fixed address/addresses (indicated on a sheet which should normally be on display close to the outlet) will stay of the form 137.138.x.x.

In addition, in order to prevent incorrectly configured private BOOTP/DHCP servers from disrupting the DHCP service, all DHCP/BOOTP requests from a system connected to a portable outlet will be directed to the Central BOOTP/DHCP server managed by IT. As a consequence, booting diskless systems such as VME boards (using BOOTP/DHCP) connected to a portable plug will NOT be supported, even if you run your own BOOTP/DHCP server. Other network broadcast packets (e.g. SUN RPC yellow page service) will also be blocked. Finally, systems acting as BOOTP/DHCP servers must NOT be connected to portable outlets.

At some future date, for network security reasons, only correctly registered computers will be allocated a DHCP address permitting the full range of access possibilities to the general CERN network. This restriction will be based on the computer hardware address (also known as MAC address, adapter address or ethernet address), so we strongly encourage all laptop users to check or register their systems at:

General help for the installation and use of portable computers may be found at

For matters related to this article please contact the author.

Vol. XXXVI, issue no 3

Last Updated on Fri Dec 07 14:18:28 CET 2001.
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