Please find the below reasoning..The Train is being extended and being re-numbered as proposed in the Rly budget..
The 11017/18 will renumbered and extended up to Puducherry as Train No.11005/11006 and routed via Jolarpettai, Katpadi, Vellore, Villupuram & To Tirunelveli as Train No.11021/11022 and routed via Dharmapuri, Erode .