X.25 339
NOTE
Configure your AUX port so that you can dial in to your router. When you get the system
prompt, type in pad x121-address, and you will get a PAD connection to your X.25 device.
Cisco routers can use X.25 in the following ways:
·
As a transport medium (a backbone) using SNA or IP devices attached to remote Cisco
routers
·
With protocol translation, where X.25 is translated to TCP/IP to permit PAD users access
to TCP/IP hosts
·
With QLLC to give remote X.25-attached controllers access to a Token Ring-attached
IBM host
NOTE
Window size and packet size belong to Layer 3 of the X.25 protocol.
WAN Data Links
From the router perspective, you typically will use either X.25 Switched Virtual Circuits
(SVCs) or Permanent Virtual Circuits (PVCs) as WAN data links, as shown in Figure 10-8.
Figure 10-8
X.25 PVC
Router A
DTE
X.25
DCE
Router B
DTE
DCE
X.25 between switches
PVC
Cloud
X.75 between switches
X.75 between switches
X.25
87200333.book Page 339 Wednesday, August 22, 2001 2:53 PM