This article was first written in October 2004 for the BeezNest technical website (http://glasnost.beeznest.org/articles/179).To use Bonding Ethernet for High-Availability (failover) on Debian (Sarge or Sid with a 2.6.x kernel [1]) you need to:
- install package ifenslave-2.6 [2]
 - make sure the real NICs kernel modules are loaded automatically
 - edit /etc/network/interfaces to look like this:
 
iface bond0 inet static
        address 10.31.1.5
        netmask 255.255.255.0
        network 10.31.1.0
        gateway 10.31.1.254
        up /sbin/ifenslave bond0 eth0 eth1
        down /sbin/ifenslave -d bond0 eth0 eth1
- comment or borrow the lines referring to your real NICs in the same file
 - add the following lines to your /etc/modprobe.d/arch/i386:
 
alias bond0 bonding options bonding mode=1 miimon=100 downdelay=200 updelay=200
[1] see HOWTO Setup Bonding Ethernet on Debian with a 2.4 kernel for 2.4.x kernels
[2] at least version 1.1.0-4 of the package, otherwise be careful ifenslave is in /usr/sbin, not /sbin