Unknown Presence in Lync 2010 and Lync 2013 co-existence

I have lync 2010 and lync 2013 in my environment. Everything was working fine except when I moved the DNS of the Lync 2013 pool to the load balancer. When I did that, users on lync2013 could see the presence of users on Lync2010 pool but not vice versa. 

I have point the Lyncdiscoverinternal.domain.com to the lync2013 pool DNS. I have opened migration ports on the load balancer but still not working. It works perfectly fine if I point the DNS of the pool to one server directly without going through the Load balancer VIP.

Am I missing anything here?

Thanks!

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