Hello Ocporbust,
this serial interface is configured for a form of tunneling called STUN
every SDLC frame that is received is placed inside a TCP segment and sent to 10.0.14.1.
It should be related to some form of IBM or mainframe networking.
STUN SDLC is most commonly used in two environments: FEP to remote controller, and AS/400 to remote controller.
see
http://www.cisco.com/en/US/tech/tk827/tk369/technologies_tech_note09186a00800b451e.shtml#stun_sdlc
Hope to help
Giuseppe