Red Hat

I have installed MRTG on my Linux 5.5 system. then i started copying data from the machine when MRTG is installed to another machine. I could see some changes in graphs.

But can't understand what does that mean?

Moreover how to see load on the system where MRTG is installed by copying files to that machine or by copying files from that machine.

Then again how do we add Router address in cfg maker command?

Please Guide me!

Linux is not at version 5.5. You are using some Red Hat variant of version 5.5. Linux is the kernel, and not owned by Red Hat. They only recently went to version 3.0 (not available in RHEL 5.x) in Linux.

Please take some time and go through documentation link:
MRTG - MRTG Documentation

For checking correct version of System, run "uname -a".
Also check /etc/*-release files, which will tell you whether you are using RHEL/Suse/CentOS etc. with current update level.

For checking while copying files, you need to monitor MRTG graphs for CPU/Memory/Network. You may be able to see sudden spike, if data transfer rate is too high for system and occupying lot of resources.