RFC connection failed

HI,

i got following error while connecting R/3 to APO by RFC connection

partner not reached (host 200.200.200.20, service sapgw00) / CPI-C error CM_PROD

ERROR partner not reached (host 200.200.200.20, service

LOCATION SAP-Gateway on host system

DETAIL NiPConnect2

CALL SO_ERROR

COMPONENT NI (network interface)

COUNTER 18

ERROR TEXT WSAEHOSTUNREACH: No route to host

ERROR NUMBER 10065

MODULE ninti.c

LINE 969

RETURN CODE -10

SUBRC 0

RELEASE 620

VERSION 36

What will be the reason?. how to rectify?