One feature that superior security features of IPv6, the security is already integrated in it. To test the security protocols, conducted tests that generally attacks occurred, the extent to which the security features in IPv6 can overcome the problems of security. In a research conducted by an IPv6 observer security, Joe Klein, 62% of the publication of IPv6 is a security gap Denial of Service (DoS). Based on these data, DoS attacks are a security hole that most published among other vulnerabilities, the most common DoS attacks and significant impact on IPv6 security. Therefore, IPv6 security will be tested against DoS attacks. The penetration test using three softwares of BackTrack 5 including denial6, smurf6, and flood_router6. Denial6 attack computational resources such as processor load and network load. In terms of availability, security, servers are attacked can still respond to ping requests. Smurf6 and flood_router6 attack computational resources in terms of availability and security. From the processor and network load rises when the server is attacked, and in terms of availability, the server can not respond to ping requests. To overcome of denial6 and smurf6 with Neighbor solicitation block on the Firewall. And to prevent flood_router6, turn off the Router Discovery service or block Router Advertisement on Firewall. IPv6 is designed with security integrated is not entirely safe, especially against DoS attacks. It must be configured to have a better security system than the default configuration.