Your path should read something like this:
1,1,2,10.10.2.15,1,0
1,S1,2,xxx.yyy.zzz.www,1,S2
Where:
1 is the backplane for the first chassis (the clx backplane always uses 1)
S1 is the slot of the 1756-ENBT in the first chassis (the first position on the left is 0, second 1,...)
2 is to go outside to the Ethernet (always 2)
xxx.yyy.zzz.www is the IP address of the 1756-ENBT in the second chassis
1 is the backplane for the second chassis (always 1 for clx)
S2 is the slot of the CLX in the second chassis (starting from left the first position is 0, second 1,...)