[ << ] [ < ] [ Home ] [ > ] [ >> ]

3. Modular Networking

• Network Modules
• Interface Handlers
• DHCP
• ADSL with PPPoE/PPPoA
• APIPA (Automatic Private IP Addressing)
• Bonding
• Bridging (802.1d support)
• MAC Address
• Tunnelling
• VLAN (802.1q support)

3.a. Network Modules

We now support modular networking scripts, which means we can easily add support for new interface types and configuration modules while keeping compatibility with existing ones.

Modules load by default if the package they need is installed. If you specify a module here that doesn't have its package installed then you get an error stating which package you need to install. Ideally, you only use the modules setting when you have two or more packages installed that supply the same service and you need to prefer one over the other.

# Prefer ifconfig over iproute2
modules="ifconfig"

# You can also specify other modules for an interface
# In this case we prefer pump over dhcpcd
modules_eth0="pump"

# You can also specify which modules not to use - for example you may be
# using a supplicant or linux-wlan-ng to control wireless configuration but
# you still want to configure network settings per ESSID associated with.
modules="!iwconfig"

3.b. Interface Handlers

We provide two interface handlers presently: ifconfig and iproute2. You need one of these to do any kind of network configuration.

ifconfig is installed by default (the net-tools package is part of the system profile). iproute2 is a more powerful and flexible package, but it's not included by default.

# emerge sys-apps/iproute2

# To prefer ifconfig over iproute2 if both are installed as openrc prefers
# to use iproute2 then
modules="ifconfig"

As both ifconfig and iproute2 do very similar things we allow their basic configuration to work with each other. For example both the below code snippet work regardless of which module you are using.

config_eth0="192.168.0.2/24"
config_eth0="192.168.0.2 netmask 255.255.255.0"

# We can also specify broadcast
config_eth0="192.168.0.2/24 brd 192.168.0.255"
config_eth0="192.168.0.2 netmask 255.255.255.0 broadcast 192.168.0.255"

3.c. DHCP

DHCP is a means of obtaining network information (IP address, DNS servers, Gateway, etc) from a DHCP server. This means that if there is a DHCP server running on the network, you just have to tell each client to use DHCP and it sets up the network all by itself. Of course, you will have to configure for other things like wireless, PPP or other things if required before you can use DHCP.

DHCP can be provided by dhclient, dhcpcd, or pump. Each DHCP module has its pros and cons - here's a quick run down.

If you have more than one DHCP client installed, you need to specify which one to use - otherwise we default to dhcpcd if available.

To send specific options to the DHCP module, use module_eth0="..." (change module to the DHCP module you're using - i.e. dhcpcd_eth0).

We try and make DHCP relatively agnostic - as such we support the following commands using the dhcp_eth0 variable. The default is not to set any of them:

• release - releases the IP address for re-use
• nodns - don't overwrite /etc/resolv.conf
• nontp - don't overwrite /etc/ntp.conf
• nonis - don't overwrite /etc/yp.conf

# Only needed if you have more than one DHCP module installed
modules="dhcpcd"

config_eth0="dhcp"
dhcpcd_eth0="-t 10" # Timeout after 10 seconds
dhcp_eth0="release nodns nontp nonis" # Only get an address

3.d. ADSL with PPPoE/PPPoA

First we need to install the ADSL software.

# emerge net-dialup/ppp

Second, create the PPP net script and the net script for the ethernet interface to be used by PPP:

# ln -s /etc/init.d/net.lo /etc/init.d/net.ppp0
# ln -s /etc/init.d/net.lo /etc/init.d/net.eth0

Be sure to set rc_depend_strict to "YES" in /etc/rc.conf.

Now we need to configure /etc/conf.d/net.

config_eth0=null (Specify your ethernet interface)
config_ppp0="ppp"
link_ppp0="eth0" (Specify your ethernet interface)
plugins_ppp0="pppoe"
username_ppp0='user'
password_ppp0='password'
pppd_ppp0="
noauth
defaultroute
usepeerdns
holdoff 3
child-timeout 60
lcp-echo-interval 15
lcp-echo-failure 3
noaccomp noccp nobsdcomp nodeflate nopcomp novj novjccomp"

rc_need_ppp0="net.eth0"

You can also set your password in /etc/ppp/pap-secrets.

# The * is important
"username"  *  "password"

If you use PPPoE with a USB modem you'll need to emerge br2684ctl. Please read /usr/portage/net-dialup/speedtouch-usb/files/README for information on how to properly configure it.

3.e. APIPA (Automatic Private IP Addressing)

APIPA tries to find a free address in the range 169.254.0.0-169.254.255.255 by arping a random address in that range on the interface. If no reply is found then we assign that address to the interface.

This is only useful for LANs where there is no DHCP server and you don't connect directly to the internet and all other computers use APIPA.

For APIPA support, emerge net-misc/iputils or net-analyzer/arping.

# Try DHCP first - if that fails then fallback to APIPA
config_eth0="dhcp"
fallback_eth0="apipa"

# Just use APIPA
config_eth0="apipa"

3.f. Bonding

For link bonding/trunking emerge net-misc/ifenslave.

Bonding is used to increase network bandwidth. If you have two network cards going to the same network, you can bond them together so your applications see just one interface but they really use both network cards.

# To bond interfaces together
slaves_bond0="eth0 eth1 eth2"

# You may not want to assign an IP to the bonded interface
config_bond0="null"

# Depend on eth0, eth1 and eth2 as they may require extra configuration
rc_need_bond0="net.eth0 net.eth1 net.eth2"

3.g. Bridging (802.1d support)

For bridging support emerge net-misc/bridge-utils.

Bridging is used to join networks together. For example, you may have a server that connects to the internet via an ADSL modem and a wireless access card to enable other computers to connect to the internet via the ADSL modem. You could create a bridge to join the two interfaces together.

# Configure the bridge - "man brctl" for more details
brctl_br0="setfd 0" "sethello 0" "stp off"

# To add ports to bridge br0
bridge_br0="eth0 eth1"

# You need to configure the ports to null values so dhcp does not get started
config_eth0="null"
config_eth1="null"

# Finally give the bridge an address - you could use DHCP as well
config_br0="192.168.0.1/24"

# Depend on eth0 and eth1 as they may require extra configuration
rc_need_br0="net.eth0 net.eth1"

3.h. MAC Address

If you need to, you can change the MAC address of your interfaces through the network configuration file too.

# To set the MAC address of the interface
mac_eth0="00:11:22:33:44:55"

# To randomize the last 3 bytes only
mac_eth0="random-ending"

# To randomize between the same physical type of connection (e.g. fibre,
# copper, wireless) , all vendors
mac_eth0="random-samekind"

# To randomize between any physical type of connection (e.g. fibre, copper,
# wireless) , all vendors
mac_eth0="random-anykind"

# Full randomization - WARNING: some MAC addresses generated by this may
# NOT act as expected
mac_eth0="random-full"

3.i. Tunnelling

You don't need to emerge anything for tunnelling as the interface handler can do it for you.

# For GRE tunnels
iptunnel_vpn0="mode gre remote 207.170.82.1 key 0xffffffff ttl 255"

# For IPIP tunnels
iptunnel_vpn0="mode ipip remote 207.170.82.2 ttl 255"

# To configure the interface
config_vpn0="192.168.0.2 peer 192.168.1.1"

3.j. VLAN (802.1q support)

For VLAN support, emerge net-misc/vconfig.

Virtual LAN is a group of network devices that behave as if they were connected to a single network segment - even though they may not be. VLAN members can only see members of the same VLAN even though they may share the same physical network.

# Specify the VLAN numbers for the interface like so
# Please ensure your VLAN IDs are NOT zero-padded
vlans_eth0="1 2"

# You can also configure the VLAN
# see for vconfig man page for more details
vconfig_eth0="set_name_type VLAN_PLUS_VID_NO_PAD"
vconfig_vlan1="set_flag 1" "set_egress_map 2 6"

# Configure the interface as usual
config_vlan1="172.16.3.1 netmask 255.255.254.0"
config_vlan2="172.16.2.1 netmask 255.255.254.0"

[ << ] [ < ] [ Home ] [ > ] [ >> ]

The contents of this document, unless otherwise expressly stated, are licensed under the CC-BY-SA-2.5 license. The Gentoo Name and Logo Usage Guidelines apply.