Networking

Automatic network configuration

Automatic network configuration has been improved with each release of RISC OS :

• RISC OS 3.6 introduced automatic network configuration using AUN network addresses (1.x.y.z).
  
• RISC OS Select release 1 introduced an option to disable this automatic allocation.
  
• RISC OS Select release 2 amalgamated this configuration, and the undocumented automatic DHCP configuration into a single configuration handled by the InetConfigure module.
  
• RISC OS Select release 3 added ZeroConf 'link local address allocation' to the dynamic address allocation.
  
• RISC OS Select release 4 extends this further by allowing the gateway and resolver addresses to be automatically configured.
  

The InetConfigure module performs all automatic address configuration facilities when the machine starts up. This facility can be configured from the desktop using the Interfaces configuration tool, or from the command line.

On a CMOS reset the default configuration selects :

• Dynamic address allocation (DHCP and ZeroConf)
  
• Enables automatic gateway discovery
  
• Enables automatic resolver discovery
  
• Enabled automatic AUN network mapping
  

Commands

  *Configure InternetIP None | AUN | Dynamic | Static <ip>/<prefix>
                      [DNS <address> | auto]
                      [GW <address> | auto]

Configures the automatic address configuration

   None    - No interface configuration
   AUN     - AUN address configuration (1.x.y.z)
   Dynamic - DHCP interface configuration
   Static  - Static address configuration using the supplied address and
             network mask prefix in bits (eg 192.168.0.100/24)
   DNS <address> - configures the default resolver to the given address
   DNS auto      - configures the default resolver to be automatically discovered
   GW <address>  - configures the gateway (default route) to be the given address
   GW auto       - configures the gateway to be automatically discovered

This command configures what automatic configuration will be applied to the first ethernet interface.

We recommend that in most network circumstances the configuration be left set to 'dynamic' and no manual configuration be made.

Dynamic network configuration

With Select 3, the selection of 'Dynamic' IP addresses will also invoke support for ZeroConf link local addressing. ZeroConf is a networking address configuration system designed by a group focused on interoperability between networked devices. It is used by various computer systems under different names. Under Windows it is known as 'Automatic private address' configuration. On Apple systems, ZeroConf underlies its 'Bonjour' (previously known as 'Rendezvous') implementation.

When activated ZeroConf will configure a private address on an aliased interface. The address configuration will not clash with other addresses on the same network and can be used safely. Should another system be connected to the local network using the same address as a ZeroConf system it will back off and reconfigure to use another address. ZeroConf will always use aliased interface 9.

In the event that no DHCP server is present on the local network the system will still have a ZeroConf (link local) address with which it may communicate with other hosts. As the link local address is never removed (except in the case of an address collision, which can only be caused by two separate networks being connected), connections established through the link local address will not become invalid if a DHCP appears on the network.

Automatic resolver configuration

The automatic resolver configuration uses a number of methods to locate a resolver on the local network. This should allow most systems which use a single gateway with a proxy DNS to discover their network address. The automatic resolver configuration will attempt to probe systems within the network to locate a DNS server. Depending on the DNS server's configuration, this may not locate the server. There is no defined way to perform this automatic resolver configuration and so the implementation is a best effort which should be suitable for most users.

If DHCP is in use and provides a resolver address, it will override the automatic configuration.

Automatic gateway configuration

The automatic gateway configuration uses the standard 'Router Discovery' protocol to locate a system on the local network which provides a router. The deployment of systems which provide a Router Discovery service is limited, but should increase as the functions of home gateways are expanded.

Automatic AUN network mapping

The AUN system implemented by NetI can be configured (separately, through *Configure NetIAutoMap) to automatically map the network addresses assigned to the local interfaces into AUN Network Mappings. See the AUNIntro document for more details about AUN networks.

This documentation is copyright 3QD Developments Ltd 2013-8 and may not be reproduced or published in any form without the copyright holders permission. RISC OS is subject to continuous development and improvement as such all information is reproduced by 3QD Developments Ltd in good faith and is believed to be correct at the time of publication E&OE. 3QD Developments Ltd cannot accept any liability for any loss or damage arising from the use of any information provided as part of the RISC OS Documentation.

HTML document version 1.02  28th October 2008