On Redhat 6.1 I have two NIC cards with 4 ports each ,when the application comes up it creates a bonded interface with one port from each NIC(for ex:eth1 and eth4) and assigns a virtual IP to that interface .My requirement is that once this interface is up all the packets going out of this machine should go through the bonded interface .

Currently to achieve this I'm changing the default gw device name to bonded interface using the ip route command.(ip route replace default via 10.3.2.1 dev INT-BOND)

On stopping the application we bringdown the bonded interface and change the default gw device name back to eth0.

This works fine but just wants to confirm that this approach is fine? Otherwise should I go with iptables/ip rules modifications?

One problem with my approach is if someone brings down the bonded interface(ifdown) manually then it removes the default gw .

Any better suggestions?

Generally you should not need any special measures. In /etc/sysconfig/network the GATEWAY option should be set to the gateway address reachable over the bond and that's all there is to it. You shouldn't view taking the bond0 up and down as any different to doing the same on eth0 for example. The bond0 IP should be the only one on that subnet, so there shoudl be no confusion to the system about what it needs to do.