I just want to clarify this response concerning DNS records (which is correct, BTW!)
You should have a total of 4 "A" records for your servers, not 3.
Two of the records are set up as normal and point (one each) to the two servers.
The other two records should both have the
SAME NAME but point one to each server. It is this latter name that you should then use in your client (and also, incidentally, in your Option 160 DNS record for AutoProvisioning).
So, for example you might have:
ic1.mydomain.com - xx.xx.xx.xx (IP)
ic2.mydomain.com - yy.yy.yy.yy (IP)
ic.mydomain.com - xx.xx.xx.xx (IP)
ic.mydomain.com - yy.yy.yy.yy (IP)
Clients would then use ic.mydomain.com (as would Option 160).
In addition, you should create SRV records for the two servers (depending on whether you use TCP, TLS or UDP for SIP, this is slightly different) and the Registration Groups for Managed IP Phones should use this SRV record.
This is all covered in the "Switchover" section of either ICCE or ICCS.
I hope that clarifies for anyone who was unsure!