The best thing to do is find out what ports your CCTV software requires open and open them to the specific PC.
I.E. you have an internet address of W.X.Y.Z (change this to what your external IP is) Then when you take this PC and you put it behind the router its IP is now A.B.C.D (well your router has to know to take ports 1,2,3 and have W.X.Y.Z pass them to A.B.C.D
THe main thing to remember is the PC on the internal side you want to set up with a STATIC address. Don't let the router give it DHCP or else someday you will see A.B.C.D is now A.B.C.E and yet again you won't be able to connect remotely.
If you want to post more speficis I.E. you internal addressing strucutre, the actual software used for the CCTV I am sure we can give more help.
I.E. you have an internet address of W.X.Y.Z (change this to what your external IP is) Then when you take this PC and you put it behind the router its IP is now A.B.C.D (well your router has to know to take ports 1,2,3 and have W.X.Y.Z pass them to A.B.C.D
THe main thing to remember is the PC on the internal side you want to set up with a STATIC address. Don't let the router give it DHCP or else someday you will see A.B.C.D is now A.B.C.E and yet again you won't be able to connect remotely.
If you want to post more speficis I.E. you internal addressing strucutre, the actual software used for the CCTV I am sure we can give more help.