Foi assim que configurei um sistema Ubuntu 10.04 LTS para interligar interfaces superiores:
iface eth0 inet manual
iface eth5 inet manual
# eth0 & eth5 form bond0 for the x.y.z.0/25 subnet
auto bond0
iface bond0 inet static
bond_miimon 100
bond_mode active-backup
bond_downdelay 200
bond_updelay 200
address x.y.z.35
netmask 255.255.255.128
network x.y.z.0
post-up ifenslave bond0 eth0 eth5
pre-down ifenslave -d bond0 eth0 eth5
auto br0
iface br0 inet static
bridge_ports bond0
address x.y.z.35
netmask 255.255.255.128
network x.y.z.0
gateway x.y.z.126