Probably depends on the topology. As long as the ports are on separate networks and the same switch can't see both ports, there should be no problem.
If both ports go to the same switch, then it might get confused about which is which and make poor routing decisions.
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Darren
Thanks for the replies. I do set it to true but I have found out that there are some systems in our network that have not set it to true and was wondering what are the side effects. As Cailin_Coilleach mentioned, they are on the same VLAN but different switches.
I am thinking that this might cause packet drops/loss/re-trans. I just need to confirm this.