Developed by the ITU in the seventies, X.25 provides connections between DTE devices (such as a router) and DCE devices (such as a CSU / DSU) in public data networks. It offers a maximum bandwidth of 64Kbps, and has been replaced by Frame Relay. X.25 uses the telephone routing scheme X.121 standard, also known as International Data Numbers, which can range up to 14 digits. This number identifies the local X.121 address for the serial interface and should be configured on the router has been enabled to X.25, in order to set up virtual circuits (each virtual circuit is identified by the X.121 address.) Lastly, we know that depending on the type of X.25 switch that is connected to the router, you may need to also determine the size of the input and output packets (default 128) and size and out of frame (defaults to 2 packets).
Basic Configuration X.25 Interface Point to Point
Int s0
Encapsulation x25
347 650 001 X25 address' *** Data Link X.121 Address
256 ips X25 '*** input packet size - Input Packet Size - default 128
X25 256 ops' *** output packet size - Output Packet Size - default 128
X25 win 5
X25 wout 5
Multipoint X.25 Interface Configuration
Int s0
Encapsulation x25
X25 address 44,598,631
Ip address 255.255.255.0 131.108.102.1
X25 map ip 131.108.102.15 broadcast 44,593,389
X25 map ip 131.108.102.29 broadcast 44,591,165
X25 131 108 102 176 44,590,712 ip broadcast map
To view the status of X.25 virtual circuits of a Cisco device, you can use the show x25 vc command. To find the IP addresses of a multi-X.25 interface, use the command show x25 map.