{"id":25,"date":"2025-07-16T13:44:55","date_gmt":"2025-07-16T04:44:55","guid":{"rendered":"https:\/\/34.64.61.65\/?p=25"},"modified":"2025-07-16T14:27:34","modified_gmt":"2025-07-16T05:27:34","slug":"%eb%84%a4%ed%8a%b8%ec%9b%8c%ed%81%ac_%ea%b4%80%eb%a6%ac%ec%99%80_%ed%8a%b8%eb%9f%ac%eb%b8%94%ec%8a%88%ed%8c%85_%ec%8b%a4%ec%a0%84_%eb%85%b8%ed%95%98%ec%9a%b0","status":"publish","type":"post","link":"https:\/\/hed-g.me\/?p=25","title":{"rendered":"\ub124\ud2b8\uc6cc\ud06c \uad00\ub9ac\uc640 \ud2b8\ub7ec\ube14\uc288\ud305 \uc2e4\uc804 \ub178\ud558\uc6b0: \ud604\uc7a5\uc5d0\uc11c \ubc14\ub85c \uc368\uba39\ub294 \ubb38\uc81c \ud574\uacb0\ubc95"},"content":{"rendered":"\n

\uc548\ub155\ud558\uc138\uc694, \uc131\uc7a5\ud558\ub294 \uac1c\ubc1c\uc790 \uc5ec\ub7ec\ubd84!<\/p>\n\n\n\n

\uc11c\ubc84\uac00 \uac11\uc790\uae30 \uc751\ub2f5\ud558\uc9c0 \uc54a\uc744 \ub54c, \ubc30\ud3ec\ud55c \uc560\ud50c\ub9ac\ucf00\uc774\uc158\uc5d0 \uc811\uc18d\uc774 \uc548 \ub420 \ub54c, \ub370\uc774\ud130\ubca0\uc774\uc2a4 \uc5f0\uacb0\uc774 \ub04a\uc5b4\uc9c8 \ub54c… \uc774\ub7f0 \uc0c1\ud669\uc5d0\uc11c \uc5ec\ub7ec\ubd84\uc740 \uc5b4\ub5bb\uac8c \ud558\uc2dc\ub098\uc694? \ub2f9\ud669\ud574\uc11c “\uc778\ud130\ub137\uc774 \uc548 \ub3fc\uc694!”\ub77c\uace0 \uc678\uce58\uae30\ubcf4\ub2e4\ub294, \uccb4\uacc4\uc801\uc73c\ub85c \ubb38\uc81c\ub97c \uc9c4\ub2e8\ud558\uace0 \ud574\uacb0<\/strong>\ud560 \uc218 \uc788\ub294 \ub2a5\ub825\uc774 \ud544\uc694\ud569\ub2c8\ub2e4.<\/p>\n\n\n\n

\uc624\ub298\uc740 \uc81c\uac00 \uc2e4\ubb34\uc5d0\uc11c \uc218\uc5c6\uc774 \uacaa\uc5c8\ub358 \ub124\ud2b8\uc6cc\ud06c \ubb38\uc81c\ub4e4\uacfc \uadf8 \ud574\uacb0 \uacfc\uc815\uc744 \ud1b5\ud574 \uc5bb\uc740 \uc2e4\uc804 \ud2b8\ub7ec\ube14\uc288\ud305 \ub178\ud558\uc6b0<\/strong>\ub97c \uacf5\uc720\ud574 \ub4dc\ub9ac\uaca0\uc2b5\ub2c8\ub2e4. \uc774\ub860\ubcf4\ub2e4\ub294 “\uc9c0\uae08 \ub2f9\uc7a5 \ubb38\uc81c\ub97c \ud574\uacb0\ud574\uc57c \ud558\ub294”<\/strong> \uc0c1\ud669\uc5d0 \ucd08\uc810\uc744 \ub9de\ucdb0 \uc124\uba85\ud558\uaca0\uc2b5\ub2c8\ub2e4!<\/p>\n\n\n\n

1. \ub124\ud2b8\uc6cc\ud06c \uc9c4\ub2e8\uc758 \uae30\ubcf8: \ub2e8\uacc4\ubcc4 \uc811\uadfc\ubc95<\/h2>\n\n\n\n

\ud83d\udea8 \uae34\uae09 \uc0c1\ud669 \ub300\uc751 \uccb4\ud06c\ub9ac\uc2a4\ud2b8<\/h3>\n\n\n\n

\ubb38\uc81c\uac00 \ubc1c\uc0dd\ud588\uc744 \ub54c \uac00\uc7a5 \uba3c\uc800 \ud574\uc57c \ud560 \uc77c\ub4e4\uc785\ub2c8\ub2e4:<\/p>\n\n\n\n

# 1. \uae30\ubcf8 \ub124\ud2b8\uc6cc\ud06c \uc778\ud130\ud398\uc774\uc2a4 \uc0c1\ud0dc \ud655\uc778\nip addr show\n# \ub610\ub294\nifconfig\n\n# 2. \uae30\ubcf8 \uac8c\uc774\ud2b8\uc6e8\uc774 \uc5f0\uacb0 \ud655\uc778\nping -c 3 $(ip route | grep default | awk '{print $3}')\n\n# 3. DNS \uc11c\ubc84 \uc5f0\uacb0 \ud655\uc778\nping -c 3 8.8.8.8\n\n# 4. \uc678\ubd80 \uc5f0\uacb0 \ud655\uc778\nping -c 3 google.com\n\n# 5. \ud3ec\ud2b8 \ub9ac\uc2a4\ub2dd \uc0c1\ud0dc \ud655\uc778\nnetstat -tuln\n# \ub610\ub294 (\ucd5c\uc2e0 \uc2dc\uc2a4\ud15c)\nss -tuln<\/code><\/pre>\n\n\n\n
\ud83d\udcca \ub124\ud2b8\uc6cc\ud06c \uc815\ubcf4 \uc218\uc9d1 \uc6d0\ub77c\uc774\ub108<\/h3>\n\n\n\n
# \uc885\ud569 \ub124\ud2b8\uc6cc\ud06c \uc0c1\ud0dc \ud655\uc778 \uc2a4\ud06c\ub9bd\ud2b8\necho \"=== \ub124\ud2b8\uc6cc\ud06c \uc778\ud130\ud398\uc774\uc2a4 ===\" && ip addr show && \necho \"=== \ub77c\uc6b0\ud305 \ud14c\uc774\ube14 ===\" && ip route show && \necho \"=== DNS \uc124\uc815 ===\" && cat \/etc\/resolv.conf && \necho \"=== \ud65c\uc131 \uc5f0\uacb0 ===\" && ss -tuln | head -10<\/code><\/pre>\n\n\n\n
2. NetworkManager vs Legacy Network: \ud604\ub300\uc801 \ub124\ud2b8\uc6cc\ud06c \uad00\ub9ac<\/h2>\n\n\n\n
NetworkManager \ud65c\uc6a9\ud558\uae30<\/h3>\n\n\n\n
\ucd5c\uc2e0 \ub9ac\ub205\uc2a4 \uc2dc\uc2a4\ud15c\uc5d0\uc11c\ub294 NetworkManager\uac00 \uae30\ubcf8\uc785\ub2c8\ub2e4. \ub3d9\uc801\uc73c\ub85c \ub124\ud2b8\uc6cc\ud06c \uc124\uc815\uc744 \ubcc0\uacbd\ud560 \uc218 \uc788\uc5b4 \ub9e4\uc6b0 \uc720\uc6a9\ud569\ub2c8\ub2e4.<\/p>\n\n\n\n
nmcli\ub85c \ube60\ub978 \ub124\ud2b8\uc6cc\ud06c \uc124\uc815<\/h4>\n\n\n\n
# \ud604\uc7ac \uc5f0\uacb0 \uc0c1\ud0dc \ud655\uc778\nnmcli connection show\n\n# \ud65c\uc131 \uc5f0\uacb0\ub9cc \ud655\uc778\nnmcli connection show --active\n\n# \uc0c8\ub85c\uc6b4 \uc815\uc801 IP \uc5f0\uacb0 \uc0dd\uc131\nnmcli connection add type ethernet con-name \"static-conn\" \n  ifname eth0 ipv4.addresses 192.168.1.100\/24 \n  ipv4.gateway 192.168.1.1 ipv4.dns 8.8.8.8 \n  ipv4.method manual\n\n# \uc5f0\uacb0 \ud65c\uc131\ud654\nnmcli connection up \"static-conn\"\n\n# DHCP \uc5f0\uacb0\ub85c \ubcc0\uacbd\nnmcli connection modify \"static-conn\" ipv4.method auto\nnmcli connection up \"static-conn\"<\/code><\/pre>\n\n\n\n
nmtui: \ud14d\uc2a4\ud2b8 \uae30\ubc18 GUI<\/h4>\n\n\n\n
# \uc9c1\uad00\uc801\uc778 \ub124\ud2b8\uc6cc\ud06c \uc124\uc815 \ub3c4\uad6c \uc2e4\ud589\nnmtui<\/code><\/pre>\n\n\n\n
\uc2e4\ubb34 \ud301: \ube60\ub978 IP \ubcc0\uacbd<\/h3>\n\n\n\n
# \uc784\uc2dc\ub85c IP \uc8fc\uc18c \ucd94\uac00 (\uc7ac\ubd80\ud305 \uc2dc \uc0ac\ub77c\uc9d0)\nsudo ip addr add 192.168.1.200\/24 dev eth0\n\n# IP \uc8fc\uc18c \uc81c\uac70\nsudo ip addr del 192.168.1.200\/24 dev eth0\n\n# \uc778\ud130\ud398\uc774\uc2a4 \ud65c\uc131\ud654\/\ube44\ud65c\uc131\ud654\nsudo ip link set eth0 down\nsudo ip link set eth0 up<\/code><\/pre>\n\n\n\n
3. \uc2e4\uc804 \ud2b8\ub7ec\ube14\uc288\ud305 \uc2dc\ub098\ub9ac\uc624<\/h2>\n\n\n\n
\uc2dc\ub098\ub9ac\uc624 1: “\uc6f9 \uc11c\ubc84\uc5d0 \uc811\uc18d\uc774 \uc548 \ub429\ub2c8\ub2e4!”<\/h3>\n\n\n\n
\uc99d\uc0c1<\/strong>: \uc6f9 \uc560\ud50c\ub9ac\ucf00\uc774\uc158\uc5d0 \uc811\uc18d\ud560 \uc218 \uc5c6\uc74c<\/p>\n\n\n\n
\uc9c4\ub2e8 \uacfc\uc815<\/strong>:<\/p>\n\n\n\n
# 1\ub2e8\uacc4: \uc11c\ube44\uc2a4 \uc0c1\ud0dc \ud655\uc778\nsudo systemctl status nginx\nsudo systemctl status apache2\n\n# 2\ub2e8\uacc4: \ud3ec\ud2b8 \ub9ac\uc2a4\ub2dd \ud655\uc778\nss -tuln | grep :80\nss -tuln | grep :443\n\n# 3\ub2e8\uacc4: \ubc29\ud654\ubcbd \ud655\uc778\nsudo firewall-cmd --list-all\nsudo iptables -L\n\n# 4\ub2e8\uacc4: \ub85c\uadf8 \ud655\uc778\nsudo tail -f \/var\/log\/nginx\/error.log\nsudo journalctl -u nginx -f<\/code><\/pre>\n\n\n\n
\ud574\uacb0 \uacfc\uc815<\/strong>:<\/p>\n\n\n\n
# \uc11c\ube44\uc2a4 \uc7ac\uc2dc\uc791\nsudo systemctl restart nginx\n\n# \ubc29\ud654\ubcbd \ud3ec\ud2b8 \uc5f4\uae30\nsudo firewall-cmd --permanent --add-service=http\nsudo firewall-cmd --permanent --add-service=https\nsudo firewall-cmd --reload\n\n# \ud3ec\ud2b8 \uc9c1\uc811 \uc5f4\uae30\nsudo firewall-cmd --permanent --add-port=8080\/tcp\nsudo firewall-cmd --reload<\/code><\/pre>\n\n\n\n
\uc2dc\ub098\ub9ac\uc624 2: “\ub370\uc774\ud130\ubca0\uc774\uc2a4 \uc5f0\uacb0\uc774 \ub04a\uc5b4\uc9d1\ub2c8\ub2e4!”<\/h3>\n\n\n\n
\uc99d\uc0c1<\/strong>: \uc560\ud50c\ub9ac\ucf00\uc774\uc158\uc5d0\uc11c DB \uc5f0\uacb0 \ud0c0\uc784\uc544\uc6c3<\/p>\n\n\n\n
\uc9c4\ub2e8 \uacfc\uc815<\/strong>:<\/p>\n\n\n\n
# 1\ub2e8\uacc4: DB \uc11c\ubc84 \uc5f0\uacb0 \ud14c\uc2a4\ud2b8\ntelnet db-server 3306  # MySQL\ntelnet db-server 5432  # PostgreSQL\n\n# 2\ub2e8\uacc4: \ub124\ud2b8\uc6cc\ud06c \uacbd\ub85c \ud655\uc778\ntraceroute db-server\nmtr db-server  # \uc2e4\uc2dc\uac04 \uacbd\ub85c \ucd94\uc801\n\n# 3\ub2e8\uacc4: DNS \ud574\uc11d \ud655\uc778\nnslookup db-server\ndig db-server\n\n# 4\ub2e8\uacc4: \uc5f0\uacb0 \ud480 \uc0c1\ud0dc \ud655\uc778\nss -tuln | grep :3306<\/code><\/pre>\n\n\n\n
\ud574\uacb0 \uacfc\uc815<\/strong>:<\/p>\n\n\n\n
# \/etc\/hosts\uc5d0 DB \uc11c\ubc84 \ucd94\uac00 (DNS \ubb38\uc81c \uc784\uc2dc \ud574\uacb0)\necho \"192.168.1.10 db-server\" | sudo tee -a \/etc\/hosts\n\n# MySQL \uc5f0\uacb0 \ud14c\uc2a4\ud2b8\nmysql -h db-server -u username -p\n\n# \uc560\ud50c\ub9ac\ucf00\uc774\uc158 \uc7ac\uc2dc\uc791\uc73c\ub85c \uc5f0\uacb0 \ud480 \ucd08\uae30\ud654\nsudo systemctl restart your-app<\/code><\/pre>\n\n\n\n
\uc2dc\ub098\ub9ac\uc624 3: “\uc778\ud130\ub137\uc740 \ub418\ub294\ub370 \ud2b9\uc815 \uc0ac\uc774\ud2b8\ub9cc \uc548 \ub429\ub2c8\ub2e4!”<\/h3>\n\n\n\n
\uc99d\uc0c1<\/strong>: \uc77c\ubc18\uc801\uc778 \uc6f9\uc0ac\uc774\ud2b8\ub294 \uc811\uc18d\ub418\uc9c0\ub9cc \ud2b9\uc815 \uc11c\ube44\uc2a4\ub9cc \uc548 \ub428<\/p>\n\n\n\n
\uc9c4\ub2e8 \uacfc\uc815<\/strong>:<\/p>\n\n\n\n
# 1\ub2e8\uacc4: DNS \ubb38\uc81c \ud655\uc778\nnslookup problematic-site.com\nnslookup problematic-site.com 8.8.8.8\n\n# 2\ub2e8\uacc4: \ub2e4\ub978 DNS \uc11c\ubc84\ub85c \ud14c\uc2a4\ud2b8\nping problematic-site.com\nping $(nslookup problematic-site.com 1.1.1.1 | grep Address | tail -1 | cut -d' ' -f2)\n\n# 3\ub2e8\uacc4: \uacbd\ub85c \ucd94\uc801\uc73c\ub85c \uc5b4\ub514\uc11c \ub9c9\ud788\ub294\uc9c0 \ud655\uc778\ntraceroute problematic-site.com\n\n# 4\ub2e8\uacc4: \ud2b9\uc815 \ud3ec\ud2b8 \uc811\uc18d \ud14c\uc2a4\ud2b8\ntelnet problematic-site.com 80\ntelnet problematic-site.com 443<\/code><\/pre>\n\n\n\n
4. \ub124\ud2b8\uc6cc\ud06c \uc131\ub2a5 \ubaa8\ub2c8\ud130\ub9c1\uacfc \ucd5c\uc801\ud654<\/h2>\n\n\n\n
\uc2e4\uc2dc\uac04 \ub124\ud2b8\uc6cc\ud06c \ubaa8\ub2c8\ud130\ub9c1<\/h3>\n\n\n\n
# 1. \ub300\uc5ed\ud3ed \uc0ac\uc6a9\ub7c9 \ubaa8\ub2c8\ud130\ub9c1\niftop  # \uc2e4\uc2dc\uac04 \ub300\uc5ed\ud3ed \uc0ac\uc6a9\ub7c9\nnethogs  # \ud504\ub85c\uc138\uc2a4\ubcc4 \ub124\ud2b8\uc6cc\ud06c \uc0ac\uc6a9\ub7c9\nnload  # \uac04\ub2e8\ud55c \ub300\uc5ed\ud3ed \ubaa8\ub2c8\ud130\ub9c1\n\n# 2. \uc5f0\uacb0 \uc0c1\ud0dc \ubaa8\ub2c8\ud130\ub9c1\nwatch -n 1 'ss -tuln | wc -l'  # \uc5f0\uacb0 \uc218 \ubcc0\ud654 \ucd94\uc801\nwatch -n 1 'netstat -an | grep ESTABLISHED | wc -l'\n\n# 3. \ud328\ud0b7 \uc190\uc2e4 \ud655\uc778\nping -c 100 google.com | tail -2<\/code><\/pre>\n\n\n\n
\ub124\ud2b8\uc6cc\ud06c \uc131\ub2a5 \ucd5c\uc801\ud654<\/h3>\n\n\n\n
# TCP \ubc84\ud37c \ud06c\uae30 \uc870\uc815\necho 'net.core.rmem_max = 16777216' | sudo tee -a \/etc\/sysctl.conf\necho 'net.core.wmem_max = 16777216' | sudo tee -a \/etc\/sysctl.conf\nsudo sysctl -p\n\n# \ub124\ud2b8\uc6cc\ud06c \uc778\ud130\ud398\uc774\uc2a4 \ud050 \ud06c\uae30 \ud655\uc778\nethtool -g eth0\n\n# MTU \ud06c\uae30 \ucd5c\uc801\ud654\nsudo ip link set dev eth0 mtu 9000  # Jumbo Frame (\uac00\ub2a5\ud55c \uacbd\uc6b0)<\/code><\/pre>\n\n\n\n
5. \uace0\uae09 \ud2b8\ub7ec\ube14\uc288\ud305 \ub3c4\uad6c\uc640 \uae30\ubc95<\/h2>\n\n\n\n
tcpdump\uc640 Wireshark\ub97c \ud65c\uc6a9\ud55c \ud328\ud0b7 \ubd84\uc11d<\/h3>\n\n\n\n
# \ud2b9\uc815 \ud3ec\ud2b8 \ud2b8\ub798\ud53d \ucea1\ucc98\nsudo tcpdump -i eth0 port 80 -w web_traffic.pcap\n\n# \ud2b9\uc815 \ud638\uc2a4\ud2b8\uc640\uc758 \ud1b5\uc2e0 \ucea1\ucc98\nsudo tcpdump -i eth0 host 192.168.1.100\n\n# HTTP \uc694\uccad\/\uc751\ub2f5 \ub0b4\uc6a9 \ud655\uc778\nsudo tcpdump -i eth0 -A port 80\n\n# SSL\/TLS \ud578\ub4dc\uc170\uc774\ud06c \ubb38\uc81c \uc9c4\ub2e8\nsudo tcpdump -i eth0 port 443 -v<\/code><\/pre>\n\n\n\n
\ub124\ud2b8\uc6cc\ud06c \uc5f0\uacb0 \ubb38\uc81c \uc790\ub3d9 \uc9c4\ub2e8 \uc2a4\ud06c\ub9bd\ud2b8<\/h3>\n\n\n\n
#!\/bin\/bash\n# network_diagnostic.sh\n\necho \"=== \ub124\ud2b8\uc6cc\ud06c \uc9c4\ub2e8 \uc2dc\uc791 ===\"\n\n# \uae30\ubcf8 \uc815\ubcf4 \uc218\uc9d1\nGATEWAY=$(ip route | grep default | awk '{print $3}')\nINTERFACE=$(ip route | grep default | awk '{print $5}')\n\necho \"\ub124\ud2b8\uc6cc\ud06c \uc778\ud130\ud398\uc774\uc2a4: $INTERFACE\"\necho \"\uae30\ubcf8 \uac8c\uc774\ud2b8\uc6e8\uc774: $GATEWAY\"\n\n# 1. \uc778\ud130\ud398\uc774\uc2a4 \uc0c1\ud0dc \ud655\uc778\necho \"1. \uc778\ud130\ud398\uc774\uc2a4 \uc0c1\ud0dc:\"\nip link show $INTERFACE | grep -E \"(state|mtu)\"\n\n# 2. IP \uc8fc\uc18c \ud655\uc778\necho \"2. IP \uc8fc\uc18c \uc124\uc815:\"\nip addr show $INTERFACE | grep inet\n\n# 3. \uac8c\uc774\ud2b8\uc6e8\uc774 \uc5f0\uacb0 \ud655\uc778\necho \"3. \uac8c\uc774\ud2b8\uc6e8\uc774 \uc5f0\uacb0 \ud14c\uc2a4\ud2b8:\"\nif ping -c 3 $GATEWAY > \/dev\/null 2>&1; then\n    echo \"\u2705 \uac8c\uc774\ud2b8\uc6e8\uc774 \uc5f0\uacb0 \uc815\uc0c1\"\nelse\n    echo \"\u274c \uac8c\uc774\ud2b8\uc6e8\uc774 \uc5f0\uacb0 \uc2e4\ud328\"\nfi\n\n# 4. DNS \ud655\uc778\necho \"4. DNS \uc5f0\uacb0 \ud14c\uc2a4\ud2b8:\"\nif ping -c 3 8.8.8.8 > \/dev\/null 2>&1; then\n    echo \"\u2705 DNS \uc11c\ubc84 \uc5f0\uacb0 \uc815\uc0c1\"\nelse\n    echo \"\u274c DNS \uc11c\ubc84 \uc5f0\uacb0 \uc2e4\ud328\"\nfi\n\n# 5. \uc678\ubd80 \uc5f0\uacb0 \ud655\uc778\necho \"5. \uc678\ubd80 \uc5f0\uacb0 \ud14c\uc2a4\ud2b8:\"\nif ping -c 3 google.com > \/dev\/null 2>&1; then\n    echo \"\u2705 \uc678\ubd80 \uc5f0\uacb0 \uc815\uc0c1\"\nelse\n    echo \"\u274c \uc678\ubd80 \uc5f0\uacb0 \uc2e4\ud328\"\nfi\n\n# 6. \uc11c\ube44\uc2a4 \ud3ec\ud2b8 \ud655\uc778\necho \"6. \uc8fc\uc694 \uc11c\ube44\uc2a4 \ud3ec\ud2b8 \uc0c1\ud0dc:\"\nfor port in 22 80 443 3306; do\n    if ss -tuln | grep \":$port \" > \/dev\/null; then\n        echo \"\u2705 \ud3ec\ud2b8 $port \ub9ac\uc2a4\ub2dd \uc911\"\n    else\n        echo \"\u2139\ufe0f  \ud3ec\ud2b8 $port \ube44\ud65c\uc131\"\n    fi\ndone\n\necho \"=== \uc9c4\ub2e8 \uc644\ub8cc ===\"<\/code><\/pre>\n\n\n\n
\uc9c0\uc18d\uc801\uc778 \ubaa8\ub2c8\ud130\ub9c1 \uc124\uc815<\/h3>\n\n\n\n
# crontab\uc5d0 \ucd94\uac00\ud560 \ubaa8\ub2c8\ud130\ub9c1 \uc2a4\ud06c\ub9bd\ud2b8\n*\/5 * * * * \/usr\/local\/bin\/network_check.sh >> \/var\/log\/network_monitor.log 2>&1\n\n# network_check.sh \uc608\uc2dc\n#!\/bin\/bash\nTIMESTAMP=$(date '+%Y-%m-%d %H:%M:%S')\nif ! ping -c 1 8.8.8.8 > \/dev\/null 2>&1; then\n    echo \"$TIMESTAMP - \ub124\ud2b8\uc6cc\ud06c \uc5f0\uacb0 \uc2e4\ud328!\" | logger -t network_monitor\n    # \uc54c\ub9bc \ubc1c\uc1a1 (\uc2ac\ub799, \uc774\uba54\uc77c \ub4f1)\n    curl -X POST -H 'Content-type: application\/json' \n        --data '{\"text\":\"\ud83d\udea8 \uc11c\ubc84 \ub124\ud2b8\uc6cc\ud06c \uc5f0\uacb0 \uc7a5\uc560 \ubc1c\uc0dd!\"}' \n        YOUR_SLACK_WEBHOOK_URL\nfi<\/code><\/pre>\n\n\n\n
6. \uc790\uc8fc \ubc1c\uc0dd\ud558\ub294 \ubb38\uc81c\uc640 \uc989\uc2dc \ud574\uacb0\ubc95<\/h2>\n\n\n\n
DNS \uce90\uc2dc \ubb38\uc81c<\/h3>\n\n\n\n
# DNS \uce90\uc2dc \ud50c\ub7ec\uc2dc (\uc2dc\uc2a4\ud15c\ubcc4)\nsudo systemctl restart systemd-resolved  # Ubuntu 18.04+\nsudo \/etc\/init.d\/nscd restart  # \uae30\ud0c0 Linux\nsudo systemctl restart NetworkManager  # \ub124\ud2b8\uc6cc\ud06c \uc7ac\uc2dc\uc791\n\n# \uc784\uc2dc DNS \uc11c\ubc84 \ubcc0\uacbd\necho \"nameserver 1.1.1.1\" | sudo tee \/etc\/resolv.conf<\/code><\/pre>\n\n\n\n
MTU \ubb38\uc81c (\ud328\ud0b7 \ud06c\uae30 \ubb38\uc81c)<\/h3>\n\n\n\n
# MTU \ud06c\uae30 \ud655\uc778\nip link show eth0 | grep mtu\n\n# \ucd5c\uc801 MTU \ud06c\uae30 \ucc3e\uae30\nping -M do -s 1472 google.com  # 1500 - 28 = 1472\n\n# MTU \uc870\uc815\nsudo ip link set dev eth0 mtu 1450<\/code><\/pre>\n\n\n\n
ARP \ud14c\uc774\ube14 \ubb38\uc81c<\/h3>\n\n\n\n
# ARP \ud14c\uc774\ube14 \ud655\uc778\nip neigh show\n\n# ARP \uce90\uc2dc \uc0ad\uc81c\nsudo ip neigh flush all\n\n# \ud2b9\uc815 \ud56d\ubaa9 \uc0ad\uc81c\nsudo ip neigh del 192.168.1.1 dev eth0<\/code><\/pre>\n\n\n\n
7. \ubcf4\uc548\uc744 \uace0\ub824\ud55c \ub124\ud2b8\uc6cc\ud06c \uad00\ub9ac<\/h2>\n\n\n\n
\ud3ec\ud2b8 \uc2a4\uce94 \uac10\uc9c0 \ubc0f \ub300\uc751<\/h3>\n\n\n\n
# \ud604\uc7ac \uc5f4\ub9b0 \ud3ec\ud2b8 \ud655\uc778\nsudo ss -tuln\n\n# \ubd88\ud544\uc694\ud55c \uc11c\ube44\uc2a4 \uc911\uc9c0\nsudo systemctl disable telnet\nsudo systemctl disable ftp\n\n# \ubc29\ud654\ubcbd \uac15\ud654\nsudo firewall-cmd --set-default-zone=drop\nsudo firewall-cmd --zone=trusted --add-source=192.168.1.0\/24\nsudo firewall-cmd --runtime-to-permanent<\/code><\/pre>\n\n\n\n
\ub124\ud2b8\uc6cc\ud06c \uc811\uadfc \ub85c\uadf8 \ubaa8\ub2c8\ud130\ub9c1<\/h3>\n\n\n\n
# SSH \uc811\uadfc \ub85c\uadf8 \ud655\uc778\nsudo grep \"Failed password\" \/var\/log\/secure\n\n# \uc2e4\uc2dc\uac04 \uc811\uadfc \ubaa8\ub2c8\ud130\ub9c1\nsudo tail -f \/var\/log\/secure | grep ssh\n\n# \ub124\ud2b8\uc6cc\ud06c \uc5f0\uacb0 \ub85c\uae45\nss -tuln > \/tmp\/connections_$(date +%Y%m%d_%H%M%S).log<\/code><\/pre>\n\n\n\n
\ub9c8\uce58\uba70: \ub124\ud2b8\uc6cc\ud06c \ud2b8\ub7ec\ube14\uc288\ud305 \ub9c8\uc2a4\ud130\uac00 \ub418\ub294 \uae38<\/h2>\n\n\n\n
\uc77c\uc77c \uccb4\ud06c\ub9ac\uc2a4\ud2b8<\/h3>\n\n\n\n
    \n
  • [ ] \uc11c\ubc84\ubcc4 \ub124\ud2b8\uc6cc\ud06c \uc5f0\uacb0 \uc0c1\ud0dc \ud655\uc778<\/li>\n\n\n\n
  • [ ] \uc8fc\uc694 \uc11c\ube44\uc2a4 \ud3ec\ud2b8 \ub9ac\uc2a4\ub2dd \uc0c1\ud0dc \ud655\uc778<\/li>\n\n\n\n
  • [ ] DNS \uc751\ub2f5 \uc2dc\uac04 \ud655\uc778<\/li>\n\n\n\n
  • [ ] \ubc29\ud654\ubcbd \ub85c\uadf8 \uac80\ud1a0<\/li>\n<\/ul>\n\n\n\n
    \uc8fc\uac04 \uccb4\ud06c\ub9ac\uc2a4\ud2b8<\/h3>\n\n\n\n
      \n
    • [ ] \ub124\ud2b8\uc6cc\ud06c \uc131\ub2a5 \uc9c0\ud45c \ubd84\uc11d<\/li>\n\n\n\n
    • [ ] \ubcf4\uc548 \uc774\ubca4\ud2b8 \ub85c\uadf8 \uac80\ud1a0<\/li>\n\n\n\n
    • [ ] \ubc31\uc5c5 \ub124\ud2b8\uc6cc\ud06c \uacbd\ub85c \ud14c\uc2a4\ud2b8<\/li>\n\n\n\n
    • [ ] \ubaa8\ub2c8\ud130\ub9c1 \uc2a4\ud06c\ub9bd\ud2b8 \uc5c5\ub370\uc774\ud2b8<\/li>\n<\/ul>\n\n\n\n
      \uae30\uc5b5\ud574\uc57c \ud560 \ud669\uae08\ub960<\/h3>\n\n\n\n
        \n
      1. \uccb4\uacc4\uc801 \uc811\uadfc<\/strong>: \ubb3c\ub9ac \u2192 \ub370\uc774\ud130\ub9c1\ud06c \u2192 \ub124\ud2b8\uc6cc\ud06c \u2192 \uc804\uc1a1 \u2192 \uc751\uc6a9 \uacc4\uce35 \uc21c\uc73c\ub85c<\/li>\n\n\n\n
      2. \ub85c\uadf8\uac00 \ub2f5<\/strong>: \ubaa8\ub4e0 \ubb38\uc81c\uc758 \ub2e8\uc11c\ub294 \ub85c\uadf8\uc5d0 \uc788\ub2e4<\/li>\n\n\n\n
      3. \uae30\ubcf8\ubd80\ud130<\/strong>: ping, telnet, nslookup \ub4f1 \uae30\ubcf8 \ub3c4\uad6c\ub97c \uc644\ubcbd\ud788 \ud65c\uc6a9\ud558\uc790<\/li>\n\n\n\n
      4. \uc608\ubc29\uc774 \ucd5c\uace0<\/strong>: \ubaa8\ub2c8\ud130\ub9c1\uacfc \uc54c\ub9bc \uccb4\uacc4\ub97c \uad6c\ucd95\ud558\uc790<\/li>\n\n\n\n
      5. \ubb38\uc11c\ud654<\/strong>: \ud574\uacb0 \uacfc\uc815\uc744 \uae30\ub85d\ud558\uc5ec \ub2e4\uc74c\uc5d0 \ud65c\uc6a9\ud558\uc790<\/li>\n<\/ol>\n\n\n\n
        \ub124\ud2b8\uc6cc\ud06c \ubb38\uc81c\ub294 \ub54c\ub85c\ub294 \ubcf5\uc7a1\ud574 \ubcf4\uc774\uc9c0\ub9cc, \uccb4\uacc4\uc801\uc73c\ub85c \uc811\uadfc\ud558\uba74 \ub300\ubd80\ubd84 \ud574\uacb0\ud560 \uc218 \uc788\uc2b5\ub2c8\ub2e4. \uc624\ub298 \ubc30\uc6b4 \ub0b4\uc6a9\ub4e4\uc744 \uc2e4\uc81c \ud658\uacbd\uc5d0\uc11c \ud558\ub098\uc529 \uc5f0\uc2b5\ud574\ubcf4\uc2dc\uace0, \uc5ec\ub7ec\ubd84\ub9cc\uc758 \ud2b8\ub7ec\ube14\uc288\ud305 \ub178\ud558\uc6b0\ub97c \uc313\uc544\uac00\uc2dc\uae38 \ubc14\ub78d\ub2c8\ub2e4!<\/p>\n\n\n\n
        \uae30\uc5b5\ud558\uc138\uc694<\/strong>: \uc88b\uc740 \ub124\ud2b8\uc6cc\ud06c \uad00\ub9ac\uc790\ub294 \ubb38\uc81c\uac00 \ubc1c\uc0dd\ud558\uae30 \uc804\uc5d0 \ubbf8\ub9ac \ub300\ube44\ud558\ub294 \uc0ac\ub78c\uc785\ub2c8\ub2e4. \ud83d\udd27<\/p>\n","protected":false},"excerpt":{"rendered":"
        \uc548\ub155\ud558\uc138\uc694, \uc131\uc7a5\ud558\ub294 \uac1c\ubc1c\uc790 \uc5ec\ub7ec\ubd84! \uc11c\ubc84\uac00 \uac11\uc790\uae30 \uc751\ub2f5\ud558\uc9c0 \uc54a\uc744 \ub54c, \ubc30\ud3ec\ud55c \uc560\ud50c\ub9ac\ucf00\uc774\uc158\uc5d0 \uc811\uc18d\uc774 \uc548 \ub420 \ub54c, \ub370\uc774\ud130\ubca0\uc774\uc2a4 \uc5f0\uacb0\uc774 \ub04a\uc5b4\uc9c8 \ub54c… \uc774\ub7f0 \uc0c1\ud669\uc5d0\uc11c \uc5ec\ub7ec\ubd84\uc740 \uc5b4\ub5bb\uac8c \ud558\uc2dc\ub098\uc694? \ub2f9\ud669\ud574\uc11c “\uc778\ud130\ub137\uc774 \uc548 \ub3fc\uc694!”\ub77c\uace0 \uc678\uce58\uae30\ubcf4\ub2e4\ub294, \uccb4\uacc4\uc801\uc73c\ub85c \ubb38\uc81c\ub97c \uc9c4\ub2e8\ud558\uace0 \ud574\uacb0\ud560 \uc218 \uc788\ub294 \ub2a5\ub825\uc774 \ud544\uc694\ud569\ub2c8\ub2e4. \uc624\ub298\uc740 \uc81c\uac00 \uc2e4\ubb34\uc5d0\uc11c \uc218\uc5c6\uc774 \uacaa\uc5c8\ub358 \ub124\ud2b8\uc6cc\ud06c \ubb38\uc81c\ub4e4\uacfc \uadf8 \ud574\uacb0 \uacfc\uc815\uc744 \ud1b5\ud574 \uc5bb\uc740 \uc2e4\uc804 \ud2b8\ub7ec\ube14\uc288\ud305 \ub178\ud558\uc6b0\ub97c \uacf5\uc720\ud574 \ub4dc\ub9ac\uaca0\uc2b5\ub2c8\ub2e4. \uc774\ub860\ubcf4\ub2e4\ub294 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[57],"tags":[59,66],"class_list":["post-25","post","type-post","status-publish","format-standard","hentry","category-network","tag-59","tag-66"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/hed-g.me\/index.php?rest_route=\/wp\/v2\/posts\/25","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/hed-g.me\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hed-g.me\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hed-g.me\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/hed-g.me\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=25"}],"version-history":[{"count":3,"href":"https:\/\/hed-g.me\/index.php?rest_route=\/wp\/v2\/posts\/25\/revisions"}],"predecessor-version":[{"id":64,"href":"https:\/\/hed-g.me\/index.php?rest_route=\/wp\/v2\/posts\/25\/revisions\/64"}],"wp:attachment":[{"href":"https:\/\/hed-g.me\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=25"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hed-g.me\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=25"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hed-g.me\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=25"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}