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File:Hamachi2 logo.PNG
Screenshot of the Hamachi Client
Developer(s) LogMeIn Inc.
Stable release / October 29, 2009; 396840799 ago
Operating system Microsoft Windows, Linux, Mac OS X
Type P2P, VPN
License Proprietary (Free for non-commercial use)
Website www.logmeinhamachi.com

Hamachi is a zero-configuration virtual private network (VPN) shareware application capable of establishing direct links between computers that are behind NAT firewalls without requiring reconfiguration (in most cases); in other words, it establishes a connection over the Internet that very closely emulates the connection that would exist if the computers were connected over a local area network. Currently available as a production version for Microsoft Windows.


Operational summary

Hamachi is a centrally-managed VPN system, consisting of the server cluster managed by the vendor of the system and the client software, which is installed on end-user computers. Client software adds a virtual network interface to a computer, and it is used for intercepting outbound as well as injecting inbound VPN traffic. Outbound traffic sent by the operating system to this interface is delivered to the client software, which encrypts and authenticates it and then sends it to the destination VPN peer over a specially initiated UDP connection. Hamachi currently handles tunneling of IP traffic including broadcasts and multicast. The Windows version also recognizes and tunnels IPX traffic.

Each client establishes and maintains a control connection to the server cluster. When the connection is established, the client goes through a login sequence, followed by the discovery process and state synchronization. The login step authenticates the client to the server and vice versa. The discovery is used to determine the topology of client's Internet connection, specifically to detect the presence of NAT and firewall devices on its route to the Internet. The synchronization step brings a client's view of its private networks in sync with other members of these networks.

When a member of a network goes online or offline, the server instructs other network peers to either establish or tear down tunnels to the former. When establishing tunnels between the peers, Hamachi uses a server-assisted NAT traversal technique, similar to UDP hole punching. Detailed information on how it works has not been made public. The vendor claims "...to successfully mediate P2P connections in roughly 95% of all cases ..." This process does not work on certain combinations of NAT devices, requiring the user to explicitly set up a port forward. Additionally 1.0 series of client software are capable of relaying traffic through vendor-maintained 'relay servers'.

In the event of unexpectedly losing a connection to the server, the client retains all its tunnels and starts actively checking their status. When the server unexpectedly loses client's connection, it informs client's peers about the fact and expects them to also start liveliness checks. This enables Hamachi tunnels to withstand transient network problems on the route between the client and the server as well as short periods of complete server unavailability.

Each Hamachi client is assigned an IP address from the address block. This address is assigned when the client logs into the system for the first time, and is henceforth associated with the client's public crypto key. As long as the client retains its key, it can log into the system and use this 5.x.x.x IP address.

The network is used to avoid collisions with private IP networks that might already be in use on the client side. Specifically -, and The address block is reserved by IANA and is not currently in use in the Internet routing domain, but this is not guaranteed to continue. The IANA free pool is expected to be exhausted by February 2011.[1] If this range is allocated, Hamachi users will not be able to connect to any Internet IP addresses within the range as long as the Hamachi client is running.

Additionally, using a separate network prefix creates a single broadcast domain between all clients. This makes it possible to use LAN protocols that rely on IP broadcasts for discovery and announcement services over Hamachi networks. Hamachi is frequently used for gaming and remote administration. The vendor provides free basic service and extra features for a fee.

In February 2007, an IP-level block was imposed by Hamachi servers on parts of Vietnamese Internet space due to "the scale of the system abuse originating from blocked addresses". The company is working on a less intrusive solution to the problem.


The following considerations apply to Hamachi's use as a VPN application:

  • Additional risk of disclosure of sensitive data which is stored or may be logged by the mediation server — minimal where data is not forwarded.
  • The security risks due to vulnerable services on remote machines otherwise not accessible behind a NAT, common to all VPNs.

Hamachi is stated to use strong, industry-standard algorithms to secure and authenticate the data and its security architecture is open[2]; the implementation, however, is closed source. An open source mediation server called Mojako[3] has been released in to the public domain, but it is still under heavy development and is not suitable for regular use at this time.

The existing client-server protocol documentation contains a number of errors[4][5], some of which have been confirmed by the vendor, pending correction[6], with others not yet confirmed.

For the product to work, a "mediation server", operated by the vendor, is required. This server stores the nickname, maintenance password, statically-allocated IP address and the associated authentication token of the user. As such, it can potentially log actual IP addresses of the VPN users as well as various details of the session.

As all peers sharing a tunnel have full "LAN-like" access to each others computers, security problems may arise if firewalls are not used, as with any insecure situation. The security features of the NAT router/firewall are bypassed; this is an issue with all VPNs.


The current builds of Hamachi are available for the following operating systems:

  • Microsoft Windows (Windows 2000, XP, Server 2003, Vista and Windows 7 only. Due to the way that Hamachi creates the virtual network adapter, Windows 95/98/ME/NT cannot be supported)
  • Linux 2.4 or newer (console-only, unofficial gui's available) (x86 and nokia770/arm binary only) (unofficial GUI front-end: hamachi-gui)
  • FreeBSD
  • Mac OS X (console-only) (claimed universal binary - in actuality is a PPC only build) (unofficial GUI front-end: HamachiX) Shimo also unofficially supports Hamachi.
  • Windows Mobile - beta

Prior to versions and for the Windows release,[7] many Windows Vista users had experienced compatibility and connection issues while using Hamachi. As of March 30, 2007, the software now includes Vista tweaks, which answer these OS-related problems, among other specific solutions. [8]

Server Load

Since Hamachi relies on a central server to process log in requests, at high traffic times users may not be able to access their Hamachi accounts.

See also

Virtual Private Networks

Network address translation


External links

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