[mrtg] Plotting multiple values in same graph

[lokesh.khanna at accelonafrica.com]

Hi All

I need some help in plotting different values in same graph.

I am polling Cisco interface for the usage. I want to achieve below
mentioned things

1. Bandwidth configured on Cisco interface. For example currently I get
total usage (in and out in bits / sec, I want to see a line in same
graph how much bandwidth is available. 
2. In same graph I want to plot a line for threshold configured. For
example I want to threshold to 80 % of total allocated bandwidth. So I
should see a threshold line. 

Pl let me know how I can do this.

Thanks - Lokesh