https://nalar.dev/tags/ipv4/ Recent content in IPv4 on Nalar Hugo en-us Tue, 15 Sep 2026 00:00:00 +0700 https://nalar.dev/arp-neighbor-cache-reuses-local-ip-to-mac-mappings/ Tue, 15 Sep 2026 00:00:00 +0700 https://nalar.dev/arp-neighbor-cache-reuses-local-ip-to-mac-mappings/ <p>Sending an IPv4 packet across an Ethernet network requires two different kinds of addresses. The IP layer selects a next-hop IPv4 address, while the Ethernet frame needs a destination MAC address that identifies the next hop on the local link.</p> <p>Address Resolution Protocol (ARP) connects those two layers. A host can ask which MAC address corresponds to a local IPv4 address, receive a reply, and store the resulting mapping. Keeping that result in a neighbor cache avoids broadcasting the same question before every packet.</p> https://nalar.dev/happy-eyeballs-races-ipv6-and-ipv4-connections/ Tue, 15 Sep 2026 00:00:00 +0700 https://nalar.dev/happy-eyeballs-races-ipv6-and-ipv4-connections/ <p>A device on a dual-stack network can often reach the same service over both IPv6 and IPv4. DNS may return <code>AAAA</code> records for IPv6 addresses and <code>A</code> records for IPv4 addresses, leaving the client with several possible routes to the destination.</p> <p>Preferring IPv6 and waiting for a complete failure before trying IPv4 sounds orderly, but it can create a visible pause when the IPv6 path is broken or unusually slow. The reverse ordering can hide IPv6 even when it offers a healthy path. Happy Eyeballs avoids both extremes by giving preferred connection attempts a short head start while allowing another address family to compete soon afterward.</p>