Exchange Coexistence DNS Entries

We are going into coexistence between exchange 2007 and exchange 2013.

Exchange 2013 Server Internal IP - 10.3.42.81

Exchange 2007 Server Internal IP - 10.3.42.51

We have assigned a public IP 86.76.156.56 on external DNS and a firewall rule that NATS

86.76.156.56 to 10.3.42.51 (Exchange 2007 Server)

Now for coexistence we need to introduce a legacy exchange host name

1. Do we need to assigne a public IP for legacy.domain.com

2. do we need to create a firewall NATing for legacy.platcorp.com where the public IP assignd above will be routed to 10.3.42.51

or

3. do we need to just modify the current firewall routing to NAT

86.76.156.56 to 10.3.42.81 (Exchange 2013 Server)







Internal DNS

Record Type Internal IP
------------------------------------------------------------

mail.domain.comA10.3.42.81

autodiscover.domain.comCNAME10.3.42.81

legacy.platcorp.comA10.3.42.51

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External DNS

Record Type Public IP
--------------------------------------------------------------------------------------

mail.domain.comA86.76.156.56

autodiscover.domain.comCNAME86.76.156.56

legacy.platcorp.comAShoud we assign a new Public IP or can we use the same public IP as 86.76.156.56

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