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Linux networking

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Armando Reis
Armando Reis

This document provides a summary of common Linux network tools including ifconfig, netstat, route, ping, traceroute, iptables, netcat, rinetd, tcpdump, and tcpreplay. It describes what each tool is used for at a high level, such as configuring network interfaces, displaying network status, manipulating network routes, testing network connectivity, implementing firewalls, and capturing/replaying network traffic. The document also provides basic introductions to IPv4 and IPv6 addressing and routing concepts.

Technology
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Linux Network Tools ,[object Object],Armando Reis - PT/DTS
[object Object],[object Object],[object Object],[object Object],What’s it all about? ,[object Object],[object Object],[object Object],[object Object]
The basics - IPv4 ,[object Object],[object Object],[object Object],[object Object]
The basics - IPv6 ,[object Object],[object Object],[object Object],[object Object],[object Object]
The basics - Addreses ,[object Object],[object Object],[object Object],[object Object],[object Object],111110110011111111111000101010010 251.63.248.170 111111111111111111111000000000000 255.255.128.0 111110110011111111111000000000000 251.63.128.0 111110110011111111111111111111111 251.63.255.255
A (very basic) routing intro ,[object Object],[object Object]
Routing intro - II ,[object Object],[object Object],[object Object]
More info? ,[object Object],[object Object],[object Object],[object Object],[object Object]
Basic network tools ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
ifconfig - Set or show network interface parameters. /sbin/ifconfig eth0 192.168.1.101 netmask 255.255.255.0 broadcast 192.168.1.255 /sbin/ifconfig -a eth0 Link encap:Ethernet HWaddr 00:1b:fc:90:ce:73 inet addr: 192.168.1.101 Bcast: 192.168.1.255 Mask: 255.255.255.0 inet6 addr: fe80::21b:fcff:fe90:ce73/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:34379438 errors:0 dropped:6 overruns:0 frame:0 TX packets:32971104 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:22215926752 (22.2 GB) TX bytes:23045492526 (23.0 GB) Interrupt:17 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:4096 errors:0 dropped:0 overruns:0 frame:0 TX packets:4096 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:212814 (212.8 KB) TX bytes:212814 (212.8 KB)
arp - Manages ‘ethernet’ addresses ,[object Object],[object Object],[object Object]
ethtool - Manages a NIC’s operating parameters. ,[object Object],[object Object],[object Object],[object Object],[object Object]
Questions?
ping - Basic testing ,[object Object],[object Object],[object Object]
route - Show or manipulate routes. asr@aqua:~$ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 213.13.144.37 192.168.1.254 255.255.255.255 UGH 0 0 0 eth0 10.135.3.51 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 10.134.15.0 0.0.0.0 255.255.255.128 U 0 0 0 ppp0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 10.135.0.0 0.0.0.0 255.255.0.0 U 0 0 0 ppp0 0.0.0.0 192.168.1.254 0.0.0.0 UG 100 0 0 eth0 asr@aqua:~$ route add -net 172.28.18.0 netmask 255.255.255.0 gw 192.168.1.250 asr@aqua:~$ route add -net 10.134.96.0 netmask 255.255.255.0 dev ppp0
netstat - Show network status. asr@aqua:~$ netstat -an Active Internet connections (servers and established)Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:4130 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4131 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4132 0.0.0.0:* LISTEN ... tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN ... tcp 1 0 192.168.1.101:52242 129.89.61.70:80 CLOSE_WAIT tcp 1 0 192.168.1.101:41412 209.85.229.147:80 CLOSE_WAIT tcp 1 0 192.168.1.101:42311 209.85.229.105:80 CLOSE_WAIT tcp 1 0 192.168.1.101:42834 130.75.116.202:80 CLOSE_WAIT ...tcp 0 0 192.168.1.101:42789 213.13.144.37:1723 ESTABLISHEDtcp 0 0 192.168.1.101:48983 74.125.4.148:80 ESTABLISHEDtcp 0 0 192.168.1.101:41347 209.85.227.102:80 ESTABLISHED Active Internet connections (servers and established)Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:4130 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4131 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4132 0.0.0.0:* LISTEN ... tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN ... tcp 1 0 192.168.1.101:52242 129.89.61.70:80 CLOSE_WAIT tcp 1 0 192.168.1.101:41412 209.85.229.147:80 CLOSE_WAIT tcp 1 0 192.168.1.101:42311 209.85.229.105:80 CLOSE_WAIT tcp 1 0 192.168.1.101:42834 130.75.116.202:80 CLOSE_WAIT ...tcp 0 0 192.168.1.101:42789 213.13.144.37:1723 ESTABLISHEDtcp 0 0 192.168.1.101:48983 74.125.4.148:80 ESTABLISHEDtcp 0 0 192.168.1.101:41347 209.85.227.102:80 ESTABLISHED
netstat - Show more network information. asr@aqua:~$ sudo netstat -antup Active Internet connections (servers and established) ... tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN 2243/portmap tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 3335/sshd tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 3517/cupsd tcp 0 0 127.0.0.1:6010 0.0.0.0:* LISTEN 9217/4 tcp 0 0 192.168.1.101:50874 213.13.144.37:1723 ESTABLISHED 7355/pptp tcp 0 144 192.168.1.101:22 192.168.1.103:51455 ESTABLISHED 9208/sshdtcp 0 0 192.168.1.101:58729 212.55.154.196:22 ESTABLISHED 7617/ssh ...tcp6 0 0 :::22 :::* LISTEN 3335/sshd udp 0 0 0.0.0.0:514 0.0.0.0:* 2506/syslogd udp 0 0 0.0.0.0:53528 0.0.0.0:* 2264/rpc.statd udp 0 0 0.0.0.0:68 0.0.0.0:* 3200/dhclient3 udp 0 0 0.0.0.0:111 0.0.0.0:* 2243/portmap ...tcp6 0 0 :::22 :::* LISTEN 3335/sshd udp 0 0 0.0.0.0:514 0.0.0.0:* 2506/syslogd udp 0 0 0.0.0.0:53528 0.0.0.0:* 2264/rpc.statd udp 0 0 0.0.0.0:68 0.0.0.0:* 3200/dhclient3 udp 0 0 0.0.0.0:111 0.0.0.0:* 2243/portmap
traceroute - Show the route between 2 hosts. ,[object Object],[object Object],[object Object]
Further reading ? ,[object Object],[object Object]
Memorize this :) http://en.wikipedia.org/wiki/File:Tcp_state_diagram_fixed.svg
More networking tools ,[object Object],[object Object],[object Object],[object Object],[object Object]
iptables ,[object Object],[object Object],[object Object]
netcat ,[object Object],[object Object],[object Object]
rinetd ,[object Object],[object Object],[object Object]
tcpdump ,[object Object],[object Object],[object Object]
tcpreplay ,[object Object],[object Object],[object Object]
Questions?
Thank you Armando Reis - PT/DTS

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Linux networking

  • 1.
  • 2.
  • 3.
  • 4.
  • 5.
  • 6.
  • 7.
  • 8.
  • 9.
  • 10. ifconfig - Set or show network interface parameters. /sbin/ifconfig eth0 192.168.1.101 netmask 255.255.255.0 broadcast 192.168.1.255 /sbin/ifconfig -a eth0 Link encap:Ethernet HWaddr 00:1b:fc:90:ce:73 inet addr: 192.168.1.101 Bcast: 192.168.1.255 Mask: 255.255.255.0 inet6 addr: fe80::21b:fcff:fe90:ce73/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:34379438 errors:0 dropped:6 overruns:0 frame:0 TX packets:32971104 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:22215926752 (22.2 GB) TX bytes:23045492526 (23.0 GB) Interrupt:17 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:4096 errors:0 dropped:0 overruns:0 frame:0 TX packets:4096 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:212814 (212.8 KB) TX bytes:212814 (212.8 KB)
  • 11.
  • 12.
  • 14.
  • 15. route - Show or manipulate routes. asr@aqua:~$ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 213.13.144.37 192.168.1.254 255.255.255.255 UGH 0 0 0 eth0 10.135.3.51 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 10.134.15.0 0.0.0.0 255.255.255.128 U 0 0 0 ppp0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 10.135.0.0 0.0.0.0 255.255.0.0 U 0 0 0 ppp0 0.0.0.0 192.168.1.254 0.0.0.0 UG 100 0 0 eth0 asr@aqua:~$ route add -net 172.28.18.0 netmask 255.255.255.0 gw 192.168.1.250 asr@aqua:~$ route add -net 10.134.96.0 netmask 255.255.255.0 dev ppp0
  • 16. netstat - Show network status. asr@aqua:~$ netstat -an Active Internet connections (servers and established)Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:4130 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4131 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4132 0.0.0.0:* LISTEN ... tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN ... tcp 1 0 192.168.1.101:52242 129.89.61.70:80 CLOSE_WAIT tcp 1 0 192.168.1.101:41412 209.85.229.147:80 CLOSE_WAIT tcp 1 0 192.168.1.101:42311 209.85.229.105:80 CLOSE_WAIT tcp 1 0 192.168.1.101:42834 130.75.116.202:80 CLOSE_WAIT ...tcp 0 0 192.168.1.101:42789 213.13.144.37:1723 ESTABLISHEDtcp 0 0 192.168.1.101:48983 74.125.4.148:80 ESTABLISHEDtcp 0 0 192.168.1.101:41347 209.85.227.102:80 ESTABLISHED Active Internet connections (servers and established)Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:4130 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4131 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4132 0.0.0.0:* LISTEN ... tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN ... tcp 1 0 192.168.1.101:52242 129.89.61.70:80 CLOSE_WAIT tcp 1 0 192.168.1.101:41412 209.85.229.147:80 CLOSE_WAIT tcp 1 0 192.168.1.101:42311 209.85.229.105:80 CLOSE_WAIT tcp 1 0 192.168.1.101:42834 130.75.116.202:80 CLOSE_WAIT ...tcp 0 0 192.168.1.101:42789 213.13.144.37:1723 ESTABLISHEDtcp 0 0 192.168.1.101:48983 74.125.4.148:80 ESTABLISHEDtcp 0 0 192.168.1.101:41347 209.85.227.102:80 ESTABLISHED
  • 17. netstat - Show more network information. asr@aqua:~$ sudo netstat -antup Active Internet connections (servers and established) ... tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN 2243/portmap tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 3335/sshd tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 3517/cupsd tcp 0 0 127.0.0.1:6010 0.0.0.0:* LISTEN 9217/4 tcp 0 0 192.168.1.101:50874 213.13.144.37:1723 ESTABLISHED 7355/pptp tcp 0 144 192.168.1.101:22 192.168.1.103:51455 ESTABLISHED 9208/sshdtcp 0 0 192.168.1.101:58729 212.55.154.196:22 ESTABLISHED 7617/ssh ...tcp6 0 0 :::22 :::* LISTEN 3335/sshd udp 0 0 0.0.0.0:514 0.0.0.0:* 2506/syslogd udp 0 0 0.0.0.0:53528 0.0.0.0:* 2264/rpc.statd udp 0 0 0.0.0.0:68 0.0.0.0:* 3200/dhclient3 udp 0 0 0.0.0.0:111 0.0.0.0:* 2243/portmap ...tcp6 0 0 :::22 :::* LISTEN 3335/sshd udp 0 0 0.0.0.0:514 0.0.0.0:* 2506/syslogd udp 0 0 0.0.0.0:53528 0.0.0.0:* 2264/rpc.statd udp 0 0 0.0.0.0:68 0.0.0.0:* 3200/dhclient3 udp 0 0 0.0.0.0:111 0.0.0.0:* 2243/portmap
  • 18.
  • 19.
  • 20. Memorize this :) http://en.wikipedia.org/wiki/File:Tcp_state_diagram_fixed.svg
  • 21.
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  • 24.
  • 25.
  • 26.
  • 28. Thank you Armando Reis - PT/DTS