Chapter 5 Configuring X2T
The X.25 to TCP switch (X2T) technology can interconnect X.25 and IP networks and
enables access between X.25 and IP hosts.
X.25 Terminal
IP Host
Router
X.25
Network
TCP/IP Network
X.25
LAPB
X.25
LAPB
Physical Layer
Physical Layer
Data Link Layer
X2T
IP
Data Link Layer
IP
TCP
TCP
Figure 5-1 Typical X2T networking
From the perspective of an X.25 host, each IP host is associated with an X.121
address. Whenever the router receives an X.25 call request packet, it examines the
destination X.121 address carried by the packet and looks in its X2T routing table for
a match for the address. If there is a matched route, the router sets up a TCP
connection with the host at the destination IP address of the X2T route. After that, the
router extracts the pure data from the X.25 packet and sends it to the IP host across
the TCP connection.
From the perspective of an IP host, it needs to know only the IP address of the
interface of the router at the IP network side to access an X.25 host. Whenever the
router receives a TCP connection request, it examines the destination IP address and
TCP port number of the TCP connection and looks up the X2T routing table for a
match. If there is a match, the router sets up an X.25 VC destined to the host at the
associated destination X.121 address of the X2T route. After that, the router extracts
the pure data from the TCP packet and sends it to the X.25 host across the X.25 VC.
5.2 X2T Configuration Tasks
Perform the following tasks to configure X2T:
Enable X.25 switching
Configure the interface at the X.25 network side
Configure the interface at the IP network side
Configure X.25 route
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