If you try connecting to, this will work too. In a web browser, go to: CUPS runs a web server on port 631, and this can be used to configure printing, regardless of what GUI you are running (or even if you are not running a GUI at all). One common, production (i.e., not just diagnostic) use of localhost on Ubuntu is to perform advanced printer configuration. TX packets:50121 errors:0 dropped:0 overruns:0 carrier:0 RX packets:50121 errors:0 dropped:0 overruns:0 frame:0
Thus, to log in as bob via SSH to the SSH server running on your own machine, you would use: ssh other network adapters, the loopback device shows up in the output of ifconfig. This IP has the hostname of localhost mapped to it. For most purposes, though, it is only necessary to use one IP address, and that is 127.0.0.1.
Addresses on Loopbackįor IPv4, the loopback interface is assigned all the IPs in the 127.0.0.0/8 address block. So if you want to experience the same site others do, the best course is usually to connect to your own server. You may be able to load the files in your browser too, though with server-side active content, it won't work the way it does when someone accesses it normally. But it is also helpful when a server offering a resource you need is running on your own machine.įor example, if you run a web server, you have all your web documents and could examine them file by file. The loopback device is sometimes explained as purely a diagnostic tool. This is important for troubleshooting (it can be compared to looking in a mirror). The loopback interface does not represent any actual hardware, but exists so applications running on your computer can always connect to servers on the same machine. When a network interface is disconnected-for example, when an Ethernet port is unplugged or Wi-Fi is turned off or not associated with an access point-no communication on that interface is possible, not even communication between your computer and itself. It is used mainly for diagnostics and troubleshooting, and to connect to servers running on the local machine. The TCP loopback fast path is enabled by the socket IOCTL SIO_LOOPBACK_FASTPATH applied to the sending and receiving sockets.The loopback device is a special, virtual network interface that your computer uses to communicate with itself.
#Ipv4 loopback driver#
This feature is turned on whenever the Socket option for fast path is set for a connection, and utilizes the optimized fast path whenever the application has opted-in and the Windows Filtering Platform (WFP) filter driver is not present for that connection. TCP loopback optimization is available on all versions of Windows Server 2012 and Windows 8. In addition, TCP loopback fast path is an optimization for newly written applications, and does not provide performance improvements for existing applications. The optimized loopback path is available for developers to programmatically control on a per-connection basis. You can observe when the connections take the slow path rather than the optimized fast path. With TCP loopback optimization, you are provided the choice to use either registered (Winsock RIO) sockets or Winsock to make use of the optimized fast path. The boundary for optimization between VMs in this case is the individual VM boundary. Because of this, VM-to-VM optimization - when both VMs are installed in the same physical host - is not provided. Loopback is defined as an inter-process communication mechanism for both processes on the same computer. The optimized loopback path works in virtualized environments. TCP loopback optimization does not cause any disparity in performance between IPv4 and IPv6 networks. TCP loopback optimization provides an optimized low-latency loopback path for performance-critical applications that rely on loopback for inter-process communication. Optimization of TCP loopback provides the following benefits: The optimized fast path increases the achievable TCP send and receive rates, and reduces latency and jitter for low latency scenarios. To address the needs of these kinds of applications, Windows Server 2012 introduces a TCP Loopback performance enhancement that provides an optimized fast path. While convenient from a development and deployment perspective, the TCP/IP loopback path can become a bottleneck for applications that require very high performance or very low latency. Many applications use the TCP/IP loopback path to provide interprocess communications. Applies To: Windows Server 2012 Transmission Control Protocol (TCP) loopback optimization