I've got bond0 setup, i've got:

alias bond0 bonding

in /etc/modprobe.conf

I've got ifcfg-bond0 setup, something along these lines:

IPADDR=172.16.1.70
NETMASK=255.255.0.0
BROADCAST=172.16.1.255
NETWORK=172.16.0.0
BOOTPROTO=none
ONBOOT=yes
USERCTL=no

(i've also got the appropriate ifcfg-eth0 and ifcfg-eth1 setup, set to slave with bond0 as the master)

Everytime I try and bring up bond0 accordingly:
$ ifup bond0

First, it says link is detected, 100baseTX, and brings up the interface, then...

I get a bunch of crap in dmesg along these lines:
bonding bond0: link status for eth0 is definitely down, disabling it
bonding bond0: link status for eth1 is definitely down, disabling it

I can ping the address of bond0 (172.16.1.70) and I can ping the loopback, but everything else is Destination Host unreachable.

Any ideas?

EDIT: Also, I ifdown bond0, rebuilt ifcfg-eth0 as if it was the only NIC, and it works fine. Which rules out the switch and cabling. Its definitely a problem w/ the bonding.

EDIT Again: Also worth noting:
[root@server_name root]# mii-tool
eth0: negotiated 100baseTx-FD, link ok
eth1: negotiated 100baseTx-FD, link ok

Bump for the morning crew. Any ideas?

Nevermind - i got it.

I just removed everything, rebooting with no interfaces and started from scratch. I think it had something to do with changing the address of the bond0 interface.

Now time to see how I can setup virtual interfaces on the bond. Fun fun

what config did you use for eth0 and eth1? im unable to get bonding to work for switch fault tolerance (nic teaming)

Have you checked the output of dmesg? What kind of problem are you having exactly? I think I've run into just about anything that could possibly go wrong.