cisco small services

TCP and UDP Small Servers

TCP and UDP small servers are servers (daemons, in Unix parlance) that run in the router which are useful for diagnostics.

The TCP small servers are:

Echo: Echoes back whatever you type through the telnet x.x.x.x echo command.
Chargen: Generates a stream of ASCII data. Use the telnet x.x.x.x chargen command.
Discard: Throws away whatever you type. Use the telnet x.x.x.x discard command.
Daytime: Returns system date and time, if it is correct. It is correct if you run Network Time Protocol (NTP), or have set the date and time manually from the exec level. Use the telnet x.x.x.x daytime command.

Replace x.x.x.x with the IP address of your router. Most routers inside Cisco run the small servers.

The UDP small servers are:

Echo: Echoes the payload of the datagram you send.
Discard: Silently pitches the datagram you send.
Chargen: Pitches the datagram you send, and responds with a 72-character string of ASCII characters terminated with a CR+LF.

Notes:

Almost all Unix boxes support the small servers listed above.
The router also offers finger service and async line bootp service, which you can independently turn off with the configuration global commands no service finger and no ip bootp server, respectively.