{"id":12116,"date":"2026-08-10T13:16:24","date_gmt":"2026-08-10T04:16:24","guid":{"rendered":"https:\/\/yorozu.cloudfree.jp\/wordpress\/?p=12116"},"modified":"2026-08-12T17:41:58","modified_gmt":"2026-08-12T08:41:58","slug":"15","status":"publish","type":"post","link":"https:\/\/yorozu.cloudfree.jp\/wordpress\/?p=12116","title":{"rendered":"15\u306e\u30cd\u30c3\u30c8\u30ef\u30fc\u30af\u57fa\u672c\u7528\u8a9e"},"content":{"rendered":"\n

\uff11\uff0e\u5168\u7a2e\u985e<\/strong><\/h4>\n\n\n\n
\"\"<\/a><\/figure>\n\n\n\n
\uff11\uff0eIP Address<\/td>1. IP Address – unique within its subnet

1. IP\u30a2\u30c9\u30ec\u30b9 – \u30b5\u30d6\u30cd\u30c3\u30c8\u5185\u3067\u4e00\u610f<\/td><\/tr>
\uff12\uff0eDNS<\/td>2. DNS – names resolve to IPs, then cache

2. DNS – \u540d\u524d\u306fIP\u30a2\u30c9\u30ec\u30b9\u306b\u89e3\u6c7a\u3055\u308c\u3001\u305d\u306e\u5f8c\u30ad\u30e3\u30c3\u30b7\u30e5\u3055\u308c\u308b<\/td><\/tr>
\uff13\uff0ePorts<\/td>3. Ports – one IP, many doors (:80, :443, :22)

3. \u30dd\u30fc\u30c8 – 1\u3064\u306eIP\u30a2\u30c9\u30ec\u30b9\u3067\u3001\u591a\u304f\u306e\u30dd\u30fc\u30c8 (:80\u3001:443\u3001:22)<\/td><\/tr>
\uff14\uff0eMAC Address<\/td>4. MAC – burned into the NIC, never leaves the LAN

4. MAC\u30a2\u30c9\u30ec\u30b9 – NIC\u306b\u713c\u304d\u4ed8\u3051\u3089\u308c\u3001LAN\u304b\u3089\u51fa\u308b\u3053\u3068\u306f\u306a\u3044<\/td><\/tr>
\uff15\uff0eNAT<\/td>5. NAT – many private IPs, one public

5. NAT – \u591a\u6570\u306e\u30d7\u30e9\u30a4\u30d9\u30fc\u30c8IP\u30a2\u30c9\u30ec\u30b9\u30681\u3064\u306e\u30d1\u30d6\u30ea\u30c3\u30afIP\u30a2\u30c9\u30ec\u30b9<\/td><\/tr>
\uff16\uff0eDHCP<\/td>6. DHCP – DISCOVER, OFFER, REQUEST, ACK

6. DHCP – DISCOVER\u3001OFFER\u3001REQUEST\u3001ACK<\/td><\/tr>
\uff17\uff0ePackets<\/td>7. Packets – split up, reassembled in order

7. \u30d1\u30b1\u30c3\u30c8 – \u5206\u5272\u3055\u308c\u3001\u9806\u756a\u306b\u518d\u69cb\u6210\u3055\u308c\u308b<\/td><\/tr>
\uff18\uff0eOSI Model<\/td>8. OSI Model – 7 layers, app down to cable

8. OSI\u30e2\u30c7\u30eb – 7\u5c64\u3001\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u304b\u3089\u30b1\u30fc\u30d6\u30eb\u307e\u3067<\/td><\/tr>
\uff19\uff0eSubnetting & CIDR<\/td>9. Subnetting – the mask splits network from host

9. \u30b5\u30d6\u30cd\u30c3\u30c8\u5316 – \u30de\u30b9\u30af\u306b\u3088\u3063\u3066\u30cd\u30c3\u30c8\u30ef\u30fc\u30af\u3068\u30db\u30b9\u30c8\u304c\u5206\u96e2\u3055\u308c\u308b<\/td><\/tr>
\uff11\uff10\uff0eRouter vs Switch<\/td>10. Router vs Switch – by IP vs by MAC

10. \u30eb\u30fc\u30bf\u30fc\u3068\u30b9\u30a4\u30c3\u30c1 – IP\u30a2\u30c9\u30ec\u30b9
\u306b\u3088\u308b\u304bMAC\u30a2\u30c9\u30ec\u30b9\u306b\u3088\u308b\u304b<\/td><\/tr>
\uff11\uff11\uff0eTCP vs UDP<\/td>11. TCP vs UDP – acked stream vs fire and forget

11. TCP\u3068UDP – ACK\u4ed8\u304d\u30b9\u30c8\u30ea\u30fc\u30e0\u304b\u3001\u9001\u4fe1\u3057\u3066\u5fd8\u308c\u308b\u65b9\u5f0f\u304b<\/td><\/tr>
\uff11\uff12\uff0eHTTP \/HTTPS<\/td>12. HTTP vs HTTPS – with or without a lock

12. HTTP\u3068HTTPS – \u30ed\u30c3\u30af\u306e\u6709\u7121<\/td><\/tr>
\uff11\uff13\uff0eTLS<\/td>13. TLS – hello, cert, key, THEN data

13. TLS – hello\u3001cert\u3001key\u3001\u305d\u3057\u3066\u30c7\u30fc\u30bf<\/td><\/tr>
\uff11\uff14\uff0eFirewall<\/td>14. Firewall – rules in order, default deny

14. \u30d5\u30a1\u30a4\u30a2\u30a6\u30a9\u30fc\u30eb – \u30eb\u30fc\u30eb\u306f\u9806\u756a\u306b\u3001\u30c7\u30d5\u30a9\u30eb\u30c8\u306f\u62d2\u5426<\/td><\/tr>
\uff11\uff15\uff0eVPN<\/td>15. VPN – a tunnel (the exit node still sees you)

15. VPN – \u30c8\u30f3\u30cd\u30eb (\u51fa\u53e3\u30ce\u30fc\u30c9\u306f\u4f9d\u7136\u3068\u3057\u3066\u3042\u306a\u305f\u3092\u8a8d\u8b58\u3057\u3066\u3044\u308b)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

\uff12\uff0e\u89e3\u8aac<\/strong><\/h4>\n\n\n\n
1. IP vs MAC is the most confused pair in networking. IP says WHERE you are on the internet. MAC says WHICH physical card you are on this cable. IP is routable and changes as you move networks. MAC is fixed and never crosses a router. Every packet carries both – and the MAC is rewritten at every hop while the IP stays put. Get that and routers, switches, ARP and traceroute all click at once.

\u7528\u8a9e\u306e\u89e3\u8aac
\u3000\u3000IP \u306f\u30a4\u30f3\u30bf\u30fc\u30cd\u30c3\u30c8\u4e0a\u306e\u3069\u3053\u306b\u3044\u308b\u304b\u3092\u793a\u3059
\u3000\u3000MAC \u306f\u3053\u306e\u30b1\u30fc\u30d6\u30eb\u4e0a\u306e\u3069\u306e\u7269\u7406\u30ab\u30fc\u30c9\u3067\u3042\u308b\u304b\u3092\u793a\u3059

\u3000\u3000IP \u306f\u30eb\u30fc\u30c6\u30a3\u30f3\u30b0\u53ef\u80fd\u3067\u3001\u30cd\u30c3\u30c8\u30ef\u30fc\u30af\u3092\u79fb\u52d5\u3059\u308b\u3068\u5909\u308f\u308b
\u3000\u3000MAC \u306f\u56fa\u5b9a\u3055\u308c\u3066\u304a\u308a\u3001\u30eb\u30fc\u30bf\u30fc\u3092\u901a\u904e\u3059\u308b\u3053\u3068\u306f\u306a\u3044

\u3000\u5168\u3066\u306e\u30d1\u30b1\u30c3\u30c8\u306b\u306f\u4e21\u65b9\u304c\u542b\u307e\u308c\u3066\u304a\u308a\u3001
\u3000\u3000MAC \u306f\u30db\u30c3\u30d7\u3054\u3068\u306b\u66f8\u304d\u63db\u3048\u3089\u308c\u308b
\u3000\u3000IP \u306f\u305d\u306e\u307e\u307e\u3067\u66f8\u304d\u63db\u3048\u3089\u308c\u306a\u3044<\/td><\/tr>
2. Most of this list is caching or translation in disguise. DNS caches name to IP. ARP caches IP to MAC. NAT translates and keeps a table to translate replies back. DHCP leases and remembers. 15 items, 3 ideas.

\u30ea\u30b9\u30c8\u306e\u307b\u3068\u3093\u3069\u306f\u3001\u507d\u88c5\u3055\u308c\u305f\u30ad\u30e3\u30c3\u30b7\u30e5\u307e\u305f\u306f\u5909\u63db
\u3000DNS \u306f\u540d\u524d\u3092 IP \u306b\u30ad\u30e3\u30c3\u30b7\u30e5\u3059\u308b
\u3000ARP \u306f IP \u3092 MAC \u306b\u30ad\u30e3\u30c3\u30b7\u30e5d\u3059\u308b
\u3000NAT \u306f\u5909\u63db\u3057\u3001\u8fd4\u4fe1\u3092\u5909\u63db\u3059\u308b\u305f\u3081\u306e\u30c6\u30fc\u30d6\u30eb\u3092\u4fdd\u6301\u3059\u308b
\u3000DHCP \u306f\u30ea\u30fc\u30b9\u3057\u3066\u8a18\u61b6\u3059\u308b<\/td><\/tr>
3. The security ones work at DIFFERENT layers – that\u2019s why you need several. A firewall filters ports and addresses. TLS encrypts payloads. A VPN wraps the lot. None replaces the others: a firewall can\u2019t see inside TLS, TLS doesn\u2019t hide WHO you\u2019re talking to, and a VPN just moves the trust boundary to whoever runs the exit node.

\u30bb\u30ad\u30e5\u30ea\u30c6\u30a3\u30fc
\u3000\u30bb\u30ad\u30e5\u30ea\u30c6\u30a3\u95a2\u9023\u306e\u3082\u306e\u306f\u3001\u7570\u306a\u308b\u30ec\u30a4\u30e4\u30fc\u3067\u52d5\u4f5c\u3057\u3001\u8907\u6570\u5fc5\u8981
\u3000\u3000\u3000\u30d5\u30a1\u30a4\u30a2\u30a6\u30a9\u30fc\u30eb\u306f\u30dd\u30fc\u30c8\u3068\u30a2\u30c9\u30ec\u30b9\u3092\u30d5\u30a3\u30eb\u30bf\u30ea\u30f3\u30b0\u3059\u308b
\u3000\u3000\u3000TLS \u306f\u30da\u30a4\u30ed\u30fc\u30c9\u3092\u6697\u53f7\u5316\u3059\u308b
\u3000\u3000\u3000VPN \u306f\u5168\u4f53\u3092\u30e9\u30c3\u30d7\u3059\u308b

\u3000\u3069\u308c\u3082\u4ed6\u306e\u30ec\u30a4\u30e4\u30fc\u306b\u53d6\u3063\u3066\u4ee3\u308f\u308b\u3082\u306e\u3067\u306f\u306a\u3044
\u3000\u3000\u3000\u30d5\u30a1\u30a4\u30a2\u30a6\u30a9\u30fc\u30eb\u306fTLS\u306e\u5185\u90e8\u3092\u898b\u308b\u3053\u3068\u306f\u3067\u304d\u306a\u3044
\u3000\u3000\u3000TLS\u306f\u901a\u4fe1\u76f8\u624b\u3092\u96a0\u3059\u3053\u3068\u3082\u3067\u304d\u306a\u3044
\u3000\u3000\u3000VPN\u306f\u4fe1\u983c\u306e\u5883\u754c\u3092\u51fa\u53e3\u30ce\u30fc\u30c9\u3092\u904b\u7528\u3059\u308b\u5074\u306b\u79fb\u3059\u3060\u3051<\/td><\/tr>
Every layer exists to translate between two things that don\u2019t speak the same language.

\u3059\u3079\u3066\u306e\u30ec\u30a4\u30e4\u30fc\u306f\u3001\u540c\u3058\u8a00\u8a9e\u3092\u8a71\u3055\u306a\u30442\u3064\u306e\u3082\u306e\u306e\u9593\u3092\u7ffb\u8a33\u3059\u308b<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

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