Protocols

• Defined in /etc/protocols
• Well known ports are defined in /etc/services

cat /etc/protocols

TCP and UDP Protocols

See tcp_ip_transport_and_applications and tcp_ip_basic

ICMP

Send two pings to server 20

ping -c2 192.168.0.120

Ping the server’s loopback interface:

ping 127.0.0.1

Send a traceroute to server 20

traceroute 192.168.0.120

Or:

tracepath 192.168.0.120

ICMPv6

• IPv6 version of ICMP
• enabled by default

Ping and ipv6 address:

ping6 

Trace a route to an IPv6 address:

tracepath6

traceroute6

Show IPv6 addresses:

ip addr | grep inet6