3Com MSR 50 Series Configuration Manual page 293

Figure 61 Interconnecting LANs via X.25
LAN 1
Router A
LAN 1 and LAN 2 communicate with each other by sending the datagrams
carrying Internet Protocol (IP) addresses. However, X.25 uses the X.121 address.
Therefore, to solve the problem, the mapping between IP address and X.121
address needs to be established. In other words, to enable X.25 to transmit data
remotely, correctly establishing the address mapping is very significant. This
section will deal with how to establish address mapping.
Create protocol to X.121 address mapping
An X.25 interface has its own X.121 address and internetworking protocol (such
as IP protocol) address. When X.25 initiates a call through this interface, the
source address (calling DTE address) in the call request packet is the X.121 address
of this interface.
Then, how can the router target the destination of the call? In other words, how
can the router determine the X.121 address for the IP address destination? For this
purpose, the router will look up the protocol-address-to-X.121 address mappings
that have been configured on the router. A direct call destination has its own
protocol address and X.121 address. In this case, a destination
protocol-address-to-X.121 address mapping must be created on the source.
Through the mapping, X.25 can find the destination X.121 address according to
the destination protocol address to initiate a call successfully. This is why the
address mapping shall be established for X.25.
n
Such a mapping should be created for every destination.
Creating PVC
A PVC can be created for the data transmission featuring large but stable traffic
size and requiring the service quality of leased line. A PVC does not need any call
process and will always exist once set up. Before creating a PVC, it is unnecessary
to create an address mapping, because an address mapping is created implicitly
when a PVC is created.
Configuration procedure
To configure X.25 datagram transmission, use the following commands:
To do...
Enter system view
Enter interface view
Create a mapping of the
destination protocol address to
X.121 address
X.25 packet
switching
network
Use the command...
system-view
interface interface-type
interface-number
x25 map protocol-type
protocol-address x121-address
x.121-address [ option ]
Configuring X.25
LAN 2
Router B
Remarks
-
-
Required
Not created by default
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