Cisco IOS Cookbook, 2nd Edition

Using STUN

Problem

You want to connect two serial devices through an IP network.

Solution

STUN provides the ability to emulate an SDLC circuit through an IP network. To simply connect two SDLC or two HDLC ports on different routers, you can use the following:

Stun-A#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Stun-A(config)#interface Loopback0
Stun-A(config-if)#ip address 10.1.15.5 255.255.255.252
Stun-A(config-if)#exit
Stun-A(config)#stun peer-name 10.1.15.5
Stun-A(config)#stun protocol-group 1 basic
Stun-A(config)#interface Serial1
Stun-A(config-if)#encapsulation stun
Stun-A(config-if)#nrzi-encoding
Stun-A(config-if)#clock rate 19200
Stun-A(config-if)#stun group 1
Stun-A(config-if)#stun route all tcp 10.1.15.9
Stun-A(config-if)#exit
Stun-A(config)#end
Stun-A#

And this router would connect this serial port to a port on a second router that is configured as follows:

Stun-B#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Stun-B(config)#interface Loopback0
Stun-B(config-if)#ip address 10.1.15.9 255.255.255.252
Stun-B(config-if)#exit
Stun-B(config)#stun peer-name 10.1.15.9
Stun-B(config)#stun protocol-group 1 basic
Stun-B(config)#interface Serial1
Stun-B(config-if)#encapsulation stun
Stun-B(config-if)#nrzi-encoding
Stun-B(config-if)#clock rate 19200
Stun-B(config-if)#stun group 1
Stun-B(config-if)#stun route all tcp 10.1.15.5
Stun-B(config-if)#exit
Stun-B(config)#end
Stun-B#

You can also do more interesting things with STUN. ...