Doh! That was easy ... I had just been reading "old" documentation, I guess from the time before the bonding driver supported 802.3ad natively? I've setup the files as per the rhel4 example, and I'm receiving an error about speed and duplex. Although both nics are connected, and the machine answers to the bond0 ip, there is no link aggregation indicated by the switch. The NICs are connected to an HP Procurve 1800. I have LACP turned on for the ports the nics are connected to. The switch indicates the protocol is enabled for those ports, but the ports are not listed as an aggregation group. from /var/log/messages Feb 2 13:23:12 vmhost ifup: Enslaving eth0 to bond0 Feb 2 13:23:13 vmhost kernel: bnx2: eth0: using MSI Feb 2 13:23:13 vmhost kernel: bonding: Warning: failed to get speed/duplex from eth0, speed forced to 100Mbps, duplex forced to Full. Feb 2 13:23:13 vmhost kernel: bonding: bond0: enslaving eth0 as an active interface with an up link. Feb 2 13:23:13 vmhost ifup: Cannot set new settings: Invalid argument Feb 2 13:23:13 vmhost ifup: not setting speed Feb 2 13:23:13 vmhost ifup: not setting duplex Feb 2 13:23:13 vmhost ifup: not setting autoneg Feb 2 13:23:13 vmhost ifup: Enslaving eth1 to bond0 Feb 2 13:23:13 vmhost kernel: bnx2: eth1: using MSI Feb 2 13:23:13 vmhost kernel: bonding: Warning: failed to get speed/duplex from eth1, speed forced to 100Mbps, duplex forced to Full. Feb 2 13:23:13 vmhost kernel: bonding: bond0: enslaving eth1 as an active interface with an up link. Feb 2 13:23:13 vmhost ifup: Cannot set new settings: Invalid argument Feb 2 13:23:13 vmhost ifup: not setting speed Feb 2 13:23:13 vmhost ifup: not setting duplex Feb 2 13:23:13 vmhost ifup: not setting autoneg Feb 2 13:23:13 vmhost network: Bringing up interface bond0: succeeded Feb 2 13:23:15 vmhost kernel: bnx2: eth0 NIC Link is Up, 1000 Mbps full duplex Feb 2 13:23:15 vmhost kernel: bnx2: eth1 NIC Link is Up, 1000 Mbps full duplex I'm not sure if it matters, or if the error itself is an error? here's the config for eth1, similar to eth0 [root at vmhost network-scripts]# cat ifcfg-eth1 DEVICE=eth1 BOOTPROTO=none HWADDR=00:18:8B:4E:A2:B1 ONBOOT=yes TYPE=Ethernet MASTER=bond0 SLAVE=yes # added this line following suggested solution for speed/duplex error ETHTOOL_OPTS="speed 1000 duplex full autoneg off" and config for bond0 [root at vmhost network-scripts]# cat ifcfg-bond0 DEVICE=bond0 IPADDR=192.168.1.6 NETMASK=255.255.255.0 NETWORK=192.168.1.0 BROADCAST=192.168.1.255 GATEWAY=192.168.1.1 ONBOOT=yes BOOTPROTO=none USERCTL=no and modprobe.conf [root at vmhost network-scripts]# cat /etc/modprobe.conf alias eth0 bnx2 alias eth1 bnx2 alias eth2 e1000 alias eth3 e1000 alias scsi_hostadapter megaraid_sas alias usb-controller ehci-hcd alias usb-controller1 uhci-hcd # modes: # mode=0 (Balance Round Robin) # mode=1 (Active backup) # mode=2 (Balance XOR) # mode=3 (Broadcast) # mode=4 (802.3ad) # mode=5 (Balance TLB) # mode=6 (Balance ALB) alias bond0 bonding options bond0 -o bond0 mode=4 miimon=500 Gordon