To achieve fail-over networking in Linux you need to bond the two NICs in Active Backup (or High-Availability) mode. Refer to Linux bonding driver documentation for more details, if needed.
Basically, to form the bonding with 2.6 kernel you need to
- install package ifenslave-2.6: (
apt-get install ifenslave-2.6)
- edit /etc/network/interfaces to form the bonding (replace values as needed):
iface bond0 inet static
up /sbin/ifenslave bond0 eth0
up /sbin/ifenslave bond0 eth3
- add the following lines to your
/etc/modprobe.d/arch/i386 to select the correct mode:
alias bond0 bonding
options bonding mode=active-backup miimon=100 downdelay=200 updelay=200
You should also make sure that the NICs' kernel modules are loaded automatically.
Concerning the firewall rules, as I don't know what kind of rules you have, maybe using
bond0 instead of
eth0 is enough?