YC.

Y connection: This setting determines what happens when channel bundling is in operation and a request for a second connection arrives.

Note: Please note that channel bundling incurs costs for two connections. No further connections can be made over LANCAPI! Only use channel bundling when the full transfer speed is required and used.
SNMP ID:
2.2.11.8 
Telnet path:
Setup > WAN > Router-Interface
Possible values:
Yes
The device interrupts channel bundling to establish the second connection to the other remote device. If the second channel becomes free again, it is automatically used for channel bundling again (always for static bundling, when required for dynamic bundling).
No
The device maintains the existing bundled connection; the second connection must wait.
Default:
Yes