5.2. External Network Configuration

The SISO router is assumed to connect to the external internet using a xDSL, Cable or ISDN connection. The IP addresses listed below need to be assinged:

These parameters can be static or dynamically assigned, as described in the next sections.

5.2.1. Static configuration

For an external interface with a fixed IP address, the following configuration files should exist:

  • resolv.conf

    • nameserver

    • nameserver

  • eth1.conf

    • BOOTPROTO=static

    • IPADDR=


  • ntpserver.conf


Examples of these files can be found at:

5.2.2. Dynamic Host Configuration Protocol (DHCP)

The Dynamic Host Configuration Protocol (DHCP) allows computers to automatically configure their network interfaces and upstream servers based on information supplied a server. It is often used by ISDN or cable routers.

DHCP client is an optional component of Busybox. For installation instructions refer to Section 3.2, “Coreutils - busybox”. To use DHCP client on the external interface, create the following configuration file:

  • /etc/sysconfig/network/eth1.conf

    • BOOTPROTO=static


Cable routers may require the hostname or client name to be passed with the DHCP Request. This can be accomplished by either



While bringing up the external network interface, SISO will start the DHCP client. Once a lease is optained, the DHCP client executes /etc/sysconfig/network/udhcpc.script to:

  1. assign the obtained IP address and netmask to the external interface

  2. write the DNS server addresses to resolv.conf, and instructs dnsmasq to reload this file.

  3. write the NTP server address to ntpserver.conf.

An example of this udhcpc.script can be found at Example D.8, “/etc/sysconfig/network/udhcpc.script”.

5.2.3. Point-to-Point Protocol over Ethernet (PPPoE)

Point-to-Point Protocol over Ethernet (PPPoE) allows authenticated sessions over Ethernet networks. It is often used by ADSL "modems".

On the SISO router, the rp-pppoe [32] plug-in provides PPPoE. This plug-in was installed in Section 4.9, “Point-to-Point Protocol (PPP)”. Note that the Linux kernel supports "kernel mode PPPoE". To use PPPoE client on the external interface, create the following configuration file:

  • /etc/sysconfig/network/eth1.conf

    • BOOTPROTO=static

I do not have access to a cable modem, but here are some general configuration notes:

  1. For PAP and CHAP the user id and password are specified in respectively /etc/sysconfig/ppp/pap-secrets and /etc/sysconfig/ppp/chap-secrets

  2. The ifup script calls calls /usr/sbin/adsl-start to initiate the PPPoE connection. For the specifics, refer to /sbin/adsl-start in the FC3 distribution or scripts/ in the rp-pppoe source.