Internet Protocols are utilized to empower the communication between the computing devices in the computer networks. IPv6 offers additional address space and more noteworthy security than IPv4. The progress from IPv4 to IPv6 has been finished through three primary change systems: dual-stack, tunneling, and translation. The IPv6 progress relies upon the similarity with the enormous introduced base of IPv4 nodes and routers just as keeping up with the security of the network from possible threats and vulnerabilities of both Internet protocols. This research identifies potential security issues in the transition mechanisms and proposing prevention mechanisms to the problems identified. Dual-Stack & Tunneling mechanisms were completely implemented in this research work and the security test was based on dual-stack network. A simulation has been designed by using GNS3 and the penetration test by the THC-IPv6 toolkit. After the implementation of simulation, IPv6 in the dual-stack mechanism was identified as vulnerable to DoS via RA flooding and IPv6 fragmentation attacks that shown the IPv6 security problems. Therefore, IPv6 ACLs and RA guards were proposed in order to protect from flooding attacks and VFR should be configured to prevent IPv6 fragmentation.