As of ESX 3.5 it was impossible to add an additional NIC to a team as active without resorting to editing the esx.conf file:

# Active and standby setup and maxActive from 1 to 2
mv /etc/vmware/esx.conf /tmp/esx.conf.bak
/bin/sed -e ’s/net\/vswitch\/child\[0001\]\/teamPolicy\/maxActive = \”1\”/net\/vswitch\/child\[0001\]\/teamPolicy\/maxActive = \”2\”/g’ /tmp/esx.conf.bak >> /etc/vmware/esx.conf

So as you can see, a “sed” command changed the maxActive from 1 to 2. But I rather not use these kinds of solutions, editing the esx.conf that is. As of ESX 3.5 U3 that’s not necessary anymore, VMware fixed this issue:

Network adapters lose bonding during scripted installation
The esxcfg-vswitch -L command now works as expected and with the same functionality as in 3.0.x.

During a scripted installation, the following two commands did not result in a bonded pair of active network adapters on virtual switch VS_VM1. Instead, vmnic3 became the active adapter and vmnic4 became the standby adapter.
esxcfg-vswitch -L vmnic3 VS_VM1
esxcfg-vswitch -L vmnic4 VS_VM1

So just use esxcfg-vswitch again and don’t edit the esx.conf anymore!