Ethernet shield rj-45 length

Is there any limit of the rj-45 cable length that is used with ethernet shield? Plannig to use >30m(100feet) cable. I mean, to avoid errors,signal fade and other things

The Ethernet shield uses the same signals as other ethernet equipment, so the maximum length is 100m but only if you use high quality cables. In my experience even 30m is too much with cheap cables but I used over 60m with high quality cables and no problems.

If you wanna got the cheap way, use shorter cables and put switches in between.

I currently have my arduino ethernet shield connected to my router with ~15m of four conductor cat3 phone wire in a 10BaseT configuration. I haven't noticed any issues, so you might want to experiment if cost or cat5 wire size is an issue.