Source: IP Reserved, Loopback and Private Addressesįor more information see What is the loopback device and how do I use it? and why is loopback IP address from 127.0.0.1 to 127.255.255.254?. 127.0.0.1 is the address most commonly used for testing purposes. Since the lower layers are short-circuited, sending to a loopback address allows the higher layers (IP and above) to be effectively tested without the chance of problems at the lower layers manifesting themselves. ![]() ![]() The purpose of the loopback range is testing of the TCP/IP protocol implementation on a host. If it's a whole class A, what is the point of other arbitrary values for the last three octets? Noĭatagram "sent" to a network 127 address should ever appear on To a network 127 address should loop back inside the host. The class A network number 127 is assigned the "loopback"įunction, that is, a datagram sent by a higher level protocol Why is there more than one loopback IP address? One key reason for this may be that some people really were wanting to help push people towards IPv6 adoption. It was decided that supporting some standards may be more desirable than helping IPv4 to limp along even more. Poke around those, or some other standards, and I'm pretty sure you can find some other large amounts of addresses that are not being super-efficiently used/allocated. The older RFC 5735 had much of the same information in a different format, e.g. To see some others: IETF BCP 153 (currently points to RFC 6890). But don't think for a minute that every last address has been used in the most effective way possible. IANA has just been handing out the addresses from the former Class A, Class B, and Class C. So, don't think that we're almost out of IPv4 addresses. Allow me to rile you up further :)Īctually, the much bigger waste of IPv4 addresses is 224/3, which contains 224/4 (minimally used for multicast) and 240/4 (almost entirely wasted, with just one address as the exception). ![]() Totally and completely unconscionable waste of spaceĪh, such strong language. (However, having unique addresses might be easier in some cases, like if you had multiple servers that could listen to the same "default" port number.) Other VPN software may also be a frequent user for such things, as Isaac Hanson referred to in his answer.) Whether you use different TCP ports on one address (there are 65,535 of them), or multiple IP addresses, makes little technical difference. But, since IANA has now reserved all of them for that purpose, there is no compelling reason for a TCP/IP stack to not support them.įor the most part, there's no compelling need for multiple addresses I often use multiple loopback connections, but can do so simply by specifying different TCP ports. ![]() If a computer has no need for more than one loopback address, or zero of them, there's no reason it has to support all those addresses. Cisco IOS supports no loopback addresses by default, but does support the loopback concept, and addresses can be manually assigned. Win95 supported 127.0.0.1 but not other 127/8 addresses. You should get a reply in the Command Prompt, which looks like this: Pinging 151.101.194. Would anyone know how to get this functionality? Thanks in advance.127/8 (shorthand for 127.0.0.0/8) is reserved by IANA. To do this, open the Command Prompt and use the following command to ping your original IP address, but type 'ping -6' to isolate the IPv6 line. I tried to set this up using port forwarding in LuCI, but it doesn't seem to work. In the scenario that I would want, all traffic from LAN to my public IP would be forwarded to the router itself (destination IP changed to 127.0.0.1), which would then redistribute it based on port forwarding rules, UPnP etc. The problem is that in my network configuration, the OpenWRT router doesn't have the public IP assigned to its WAN interface, because it sits behind an ISP router with 1:1 NAT.įrom my understanding, that means that it can't know that traffic to this public IP is in fact destined towards it, and proceeds to route it to the ISP router, which probably throws it away. from phone carrier), it works as it should, but the request times out if I try to do it from within.įrom searching on the internet, it seems that this problem is quite common, and the solution always is to enable some loopback/reflection of router WAN IP to LAN. If I try to ping/access some service on my public IP from outside of LAN (i.e. I recently got a new ISP and I am now facing an issue with accessing my own (static) public IP from within the network.
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