This appeared to be a strange entry in my logs. I show that a Verizon IP tried to retrieve my robots.txt page and received a code 206 for partial content. Isn't a code 206 supposed to be an error code for a multi-element page? How does a single element page return a code 206? Every other robot that hits the page gets a code 200 or code 304.
200-series codes are not error codes. 206 means the client asked for and received only partial content. However, that request coming from a Verizon IP would cause me to block that IP in the absence of any other knowledge.