There's more to localhost than 127.0.0.1

The loopback interface is most familiarly encountered as 127.0.0.1 and is referred to as the local loopback address. This address is present on every IPv4 host and is given the hostname localhost. What people either don't know or seem to forget is that on the lo interface, there's ~16 million other addresses that applications can also listen on. This means that you can have multiple local services on the same port; as long as they are listening on a dfiferent address. The local loopback address is not a single address, it's the range 127.0.0.1…

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Network Basics: The DHCP client

So what is DHCP? How automatic configuration works The DHCP client When you bring your laptop over to your buddies house and plug into their network, your internet is ready by "magic". This is achieved by the DHCP client daemon dhcpcd. When a new network link comes on line (e.g plugging in an ethernet cable, or connecting over WiFi), your machine sends announces itself to all devices on the link, and, if present, a DHCP server (usually the network's router) replies back, informing your computer of the settings for the particular network, and reserves you an IP…

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Network basics: Link Local Addressing and 169.254.x.x

What are those 169.254.x.x addresses all about? An look at IPv4 Link Local Addressing Earlier, we looked at DHCP. A familiar experience of troubleshooting networks is that when something breaks, Windows spends a while trying to connect, and eventually gives a seemingly meaningless address in the range of 169.254.xx.xx. Why does it do this? What are these addresses? Are they useful? The IANA (the international body that governs internet numbering and addressing) has reserved the range 169.254.0.0 - 169.254.255.255 as "link local address space". When Windows…

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