For network engineering, following short-term courses may be useful:-
(a) Diploma in Computer Application and Network Administration
(b) Certificate Course in Network Administration
National Institute of Electronics & Information Technology, Ministry of Electronics & Information Technology, Government of India (website: http://beta.nielit.gov.in) conducts these courses in various cities and towns of India. These courses are recognized. Many organizations/training institutes in private sector also offer similar types of short-term courses.
However, it would not be advisable to resign considering the present less than satisfactory employment condition in IT sector. You may undergo part-time training programme in network administration, start applying for new job and resign only after you receive a better job offer in your preferred area of work, i.e., network engineering.
"If you are killed in action, you go to Heaven. If you win, you rule this Earth (as beautiful as Heaven). That is why, O son of Kunti, take a firm resolve and fight!"-- Shrimad Bhagwad Gita