# Sites with Multiple Stacks

If the system uses multiple TCP/IP stacks, insert the following JCL statement before the Substation ES application execution steps:

`//TCAFF EXEC PROC=TIBTCAFF,STACK=TCPIP-STACK-NAME`

This statement identifies the stack that the application uses.

You can specify a TCP/IP stack at the ESB level. To use this facility, you must first set the ESB parameter STACK-NAME to the address space default. The specified STACK-NAME value is the TCP/IP stack that is used for all ESB connections with a blank TCPIP Stack Name value. If the TCPIP Stack Name value of the ESB connection is not blank, the value given there is the name used. This allows a single Substation ES to use multiple TCP/IP stacks from the same address space.

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