Cisco certifications are among the most popular in the computer networking and routing area. Some of the leading certifications offered by Cisco are:
Cisco Certified Network Associate:
     This is a foundation level certification and the most popular Cisco certification. Getting CCNA certified ensures that the candidate has enough knowledge to plan, configure, and operate simple routed WAN, switched LAN and VPN networks using Cisco products. No pre-qualification is necessary to take CCNA exam.  640-801 is the only exam necessary to pass for obtaining CCNA certification. More information on CCNA Certification exam.
Cisco Certified Network Professional:
     This is a next level certification offered by Cisco. Getting CCNP certified ensures that the candidate is knowledgeable to plan, configure, and operate routed WAN, switched LAN, and Remote Access networks using Cisco products. CCNP covers the routed protocols including TCP/IP, IPX, and AppleTalk. The routing protocols covered under CCNP include RIP v1, RIP v2, IGRP, EIGRP, OSPF, IS-IS, BGP (bcertification.anandsoft.com - Comptia Certification training, and mock exams.oth iBGP and eBGP), AppleTalk, and IPX routing. CCNP certified professionals can work with complex (100 - 500 nodes) LAN/WAN technologies including Ethernet, Token Ring, FDDI, X.25, Frame Relay, and ATM. More information on CCNP Certification exams
Cisco Certified Internetwork Expert:
     CCIE is considered hard to achieve, and CCNP is a pre-requisite for obtaining CCIE certification. CCIE consists of CCIE written, and CCIE lab exam.

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You can obtain the practice tests for Cisco certifications here. Read complete CCNA Tutorial