3Com Router User Manual

Configure X.25207
Configure X.25 
Datagram TransmissionThe configuration of X.25 datagram transmission includes:
■Create the mapping from the protocol address to X.121 address
■Create the permanent virtual circuit
In the most frequently used X.25 service, data is transmitted remotely between 
two hosts using the X.25 protocol via X.25 public packet network. As shown in 
the figure below, LAN A and LAN B are far apart, and X.25 packet switching 
network can be used to realize information exchange between...

208CHAPTER 16: CONFIGURING LAPB AND X.25
process and it always exists. An address mapping will be created implicitly while a 
permanent virtual circuit is created.
To create/delete a permanent virtual circuit, perform the following tasks in 
interface view.
Ta b l e 247   Create/Delete permanent virtual circuit
The format of this command shows that while a permanent virtual circuit is 
created, an address mapping is also created for it. Similarly, the protocol-address 
and x.121-address in the command...

Configure X.25209
Ta b l e 248   Specify/Cancel SVC maximum idle time
By default, the value of SVC maximum idle time is 0 minute, which means this 
SVC will not be disconnected for idle times out.
2Configure the maximum number of SVCs that are associated with the same 
address mapping
The maximum number of virtual circuits to be set up on the same address 
mapping can be specified. The X.25 of the 3Com Router series can establish up to 
8 virtual circuits on one address mapping. In case of large traffic...

210CHAPTER 16: CONFIGURING LAPB AND X.25
Ta b l e 250   Specify/Cancel packet pre-acknowledgement
By default, the number of pre-acknowledged packets is 0.
4Configure X.25 user facility
X.25 protocol defines various user facility options. The user can choose and 
configure the facilities. These configurations can be modified in two ways:
Configuration based on X.25 interface (use x25 call-facility..... 
command); configuration based on address mapping (use 
x25 map...... 
command).
The configuration based...

Configure X.25211
window-size and packet-size options are also supported in x25 pvc command. 
However, in 
x25 pvc command, these two options specify the window size and 
maximum packet length of the set PVC. If these two options are not selected in 
the 
x25 pvc command, the set PVC will choose the default value of X.25 
interface.
name is the name of the ROA ID list configured by the command x25 roa-list in 
the system view, for example:
[Router]x25 roa-list list1 12 34 567
In the serial port view,...

212CHAPTER 16: CONFIGURING LAPB AND X.25
Generally, inter-network protocols will need to send some broadcast datagrams 
for specific purposes. On the broadcasting physical networks (such as Ethernet), 
such requirements are naturally supported. But for non-broadcasting networks like 
X.25, how to realize the broadcasting?
The X.25 of the 3Com Router series can enable this to decide if the broadcast 
packet should be duplicated and sent to a destination. This is very important. For 
instance, the...

Configure X.25213
Configure X.25 
Sub-InterfaceX.25 sub-interface is a virtual interface with its own protocol address and virtual 
circuit. Multiple sub-interfaces can be created on a physical interface, so the 
networks can be interconnected via one physical interface. The sub-interface of 
X.25 falls into two types: point-to-point sub-interface, used to connect a single 
remote end and point-to-multipoint sub-interface, used to connect multiple 
remote ends in the same network segment. All the...

214CHAPTER 16: CONFIGURING LAPB AND X.25
Figure 64   X.25 switching networking diagram
1Enable or disable X.25 switching
In the system view, perform the following task to enable or disable X.25 switching.
Ta b l e 257   Enable or disable X.25 switching
Add or delete a PVC route
Ta b l e 258   Add or delete a PVC route
After configuration, the display x25 switch-vc-table pvc command can be 
used to show the virtual circuit route table.
2Add/Delete an SVC route
In the system view, the commands in the...

Configure X.25215
which guarantees no occurrence of link overload when an address is accessed by a 
large number of subscribers.
X.25 load balancing is provided by DCEs. In order to implement the load balancing 
in X.25 networks, a group of DTE/DCE interfaces (synchronous serial interfaces or 
XOT Tunnels) need to be configured at the remote DCE on the network as a hunt 
group. And it is necessary to allocate an X.121 address to such hunt group. When 
other equipment in the network accesses the DTE...

216CHAPTER 16: CONFIGURING LAPB AND X.25
Figure 65   Diagram of X.25 network load balancing
As shown in the above figure, Server A and Server B concurrently provide 
subscribers with identical services. They are configured as a hunt group named 
hg1. Server A and Server B have the same address of 9999 and the hunt group 
address is 8888. Enable the function of destination address substitution on Router 
RouterA for changing calls connected to address 8888 to calls connected to 
address 9999. When a...