Java - UnknownHostException

Alguien sabe porque se puede producir esta excepcion?

Gracias.

java.net.UnknownHostException: 193.144.27.121, 192.112.247.142
at java.net.InetAddress.getAllByName0(InetAddress.java:571)
at java.net.InetAddress.getAllByName0(InetAddress.java:540)
at java.net.InetAddress.getByName(InetAddress.java:472)
at weblogic.servlet.internal.ServletRequestImpl.getRemoteAddr(ServletRequestImpl.java:840)
at weblogic.servlet.logging.CLFLogger.log(CLFLogger.java:54)
at weblogic.servlet.logging.LogManagerHttp.log(LogManagerHttp.java:293)
at weblogic.servlet.internal.HttpServer.log(HttpServer.java:670)
at weblogic.servlet.internal.ServletResponseImpl.send(ServletResponseImpl.java:851)
at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:1636)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:137)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)