CCNA certification refers to having certain network knowledge and providing services for small and medium-sized enterprises. As professionals certified by CCNA, they will be able to install, debug and operate local area network (LAN), wide area network (WAN) and dial-up network services. Suitable for small networks (usually 100 nodes or less). Can operate IP at the same time; IGRP； OSPF； Serialization; EIGRP Frame Relay; IPRIPVLANsRIP Ethernet; Access lists and other network protocols. The new CCNA course adds wireless knowledge.

CCNA's famous textbook is CCNA Learning Guide. This book has been published in the fifth edition, but it is quite thick. Over 500 pages. /showthread.php？ T= 149 147 download

There are Chinese and English versions. If you have perseverance and a little network foundation, of course, you can read the English version directly. If you don't understand, you can also look at it in combination with the question bank.