Customers who have both legacy meetings server and new 8.5 meetings server can redirect "classic" meetings to 8.5 meeting rooms. For configuring the redirection, there are 2 steps procedure available as described below.
Step 1:
Configuration of Sametime 8.5 Meetings Server:
Sametime Online Meeting Toolkit (OMT) offers a REST (Representational State Transfer) API into the classic meeting server. This has been available since Sametime 7.5.1. The Sametime 8.5 Meeting Server uses the OMT to transfer meeting data from the Classic Meeting Server to it. The Sametime 8.5 server must be configured to be associated with its peer classic server.
The Sametime administrator should use the SSC’s (Sametime System Console) User Interface (UI) to enter the following key/values:
Sametime System Console portlets are available in the url => http://:8700/ibm/console
1. Click Sametime System Console in the left
2. Click Sametime servers
3. Select Sametime Meeting Servers
4. Click the registered Sametime Meeting Server in the list.
5. Add a new custom configuration key and value as follows
Configuration Key | Configuration Value |
restapi.migrationUrl | For Classic: http:///servlet/meeting/
For Enterprise Meeting Server 8.0: http:///iwc/sametime/meeting/ |

Step2:
Configuration of Sametime Legacy Server:
The URL redirection documents can be added in Sametime classic server several ways: Using a Notes client, administration client or web browser, domino administrator can access the names.nsf on the Sametime server.
Once names.nsf is accessed, the redirection documents can be added by opening the view:
Configuration --> Servers --> All Server Documents
Select the server in the list and click in the toolbar at the top of the view:
Web --> Create URL/Mapping Redirection
A new page will display allowing for the input of the redirection/mapping information. On the "Basics" tab of the page select "URL --> Redirection URL". On the "Mapping" tab enter the URLs in the "Incoming URL path:" and "Redirection URL string:" as described in the text below.
The redirection documents can be added in stages, depending on which part of the Sametime "classic" ui is desired to be redirected. For example, if a customer wants to continue to allow users to attend previously scheduled meetings, but also wants any new meetings to be created as rooms using the 8.5 ui, then only the following redirection document mapping needs to be created:
/stconf.nsf/frmConference*
[http://host_name
:/stmeetings/*]
To only redirect users that access the Sametime "classic" welcome page, then the following mapping needs to be created:
/stcenter.nsf*
[http:///stmeetings/*]
To redirect urls that are directly to individual Sametime meetings, create the following mapping:
/stconf.nsf/meeting/*
[http:///stmeetings/migration.jsp?mid=*]
To redirect all other urls paths in stconf.nsf to the new 8.5 ui, the following mapping is required:
/stconf.nsf*
[http:///stmeetings/*]
To redirect invited server urls, for a particular server, the redirect document needs to be directed at a designated server where the rooms will be created. This is to avoid creating rooms on different servers within the deployment that do not know about each other.
/stconf.nsf/WebLookupMeeting?OpenAgent&mid=* [http:///stmeetings/migration.jsp?mid=*]

Important Note:
If you have STMUX running on your Sametime 8.0.x server, make sure the following setting has been added to your sametime.ini file:
VPMX_HTTP_REDIRECT_ENABLE_RELATIVE=0
If this is not set the STMUX will modify the redirection url prior to returning it to the browser causing the url to be incorrect and resulting in a 404 error.
Reference:
http://www.ibm.com/developerworks/lotus/documentation/sametime/index.html?S_TACT=105AGX13&S_CMP=LP#toolkits