I have a scenariowith aclusterofIMand Presence10.X (two nodes) andPartitionedIntradomainFederationwithMSLync.
With respect to high availability, Cisco documentation says that the traffic between MS Lync (front end server) e IM and Presence cluster, is need a load balancer because Microsoft servers support configuration of only a single SIP static route for each domain, which means that the static route can point to just a single IM and Presence Service node.
Why can not use DNS SRV in this case (MSLyncforIMand Presence)?
Since the static route in Lync doesnt support it. You can only do FQDNs. Can we do DNS load balancing, theoretically yes but if one host is down, it doesnt failover. SIP traffic in general is not supported with load balancers so that option is off as well.