Connecting the router to X.25 public packet network
Network requirements
As shown in Figure 138, Router A, Router B, and Router C are connected to the same X.25 network. The requirements are:
The IP addresses of the interfaces Serial 2/0 of the three routers are 168.173.24.1/24, 168.173.24.2/24, and 168.173.24.3/24.
The X.121 addresses assigned to the three routers are 30561001, 30561002, and 30561003.
The standard window size supported by the packet network: both receiving window and sending window are 5.
The standard maximum packet size: both the maximum receiving packet size and the maximum sending packet size are 512.
Channel range: permanent virtual circuit range, incoming-only channel range and outgoing-only channel range are disabled, and two-way channel range is [1, 32].
Figure 138: Network diagram
![](images/image134.png)
Configuration procedure
Configure Router A:
# Assign an IP address for the interface.
<RouterA> system-view [RouterA] interface serial 2/0 [RouterA-Serial2/0] ip address 168.173.24.1 255.255.255.0
# Access the public packet network, and configure the router to operate in DTE mode.
[RouterA-Serial2/0] link-protocol x25 dte [RouterA-Serial2/0] x25 x121-address 30561001 [RouterA-Serial2/0] x25 window-size 5 5 [RouterA-Serial2/0] x25 packet-size 512 512 [RouterA-Serial2/0] x25 vc-range bi-channel 1 32 [RouterA-Serial2/0] x25 map ip 168.173.24.2 x121-address 30561002 [RouterA-Serial2/0] x25 map ip 168.173.24.3 x121-address 30561003 [RouterA-Serial2/0] shutdown [RouterA-Serial2/0] undo shutdown
Configure Router B:
# Assign an IP address for the interface.
<RouterB> system-view [RouterB] interface serial 2/0 [RouterB-Serial2/0] ip address 168.173.24.2 255.255.255.0
# Access the public packet network, and configure the router to operate in DTE mode.
[RouterB-Serial2/0] link-protocol x25 dte [RouterB-Serial2/0] x25 x121-address 30561002 [RouterB-Serial2/0] x25 window-size 5 5 [RouterB-Serial2/0] x25 packet-size 512 512 [RouterB-Serial2/0] x25 vc-range bi-channel 1 32 [RouterB-Serial2/0] x25 map ip 168.173.24.1 x121-address 30561001 [RouterB-Serial2/0] x25 map ip 168.173.24.3 x121-address 30561003 [RouterB-Serial2/0] shutdown [RouterB-Serial2/0] undo shutdown
Configure Router C:
# Assign an IP address for the interface.
<RouterC> system-view [RouterC] interface serial 2/0 [RouterC-Serial2/0] ip address 168.173.24.3 255.255.255.0
# Access the public packet network, and configure the router to operate in DTE mode.
[RouterC-Serial2/0] link-protocol x25 dte [RouterC-Serial2/0] x25 x121-address 30561003 [RouterC-Serial2/0] x25 window-size 5 5 [RouterC-Serial2/0] x25 packet-size 512 512 [RouterC-Serial2/0] x25 vc-range bi-channel 1 32 [RouterC-Serial2/0] x25 map ip 168.173.24.1 x121-address 30561001 [RouterC-Serial2/0] x25 map ip 168.173.24.2 x121-address 30561002 [RouterC-Serial2/0] shutdown [RouterC-Serial2/0] undo shutdown
Verifying the configuration
Ping Router B and Router C from Router A. Check that Router A can reach Router B and Router C.
# Display the X.25 address mapping table on Router A, for example.
[RouterA-Serial2/0] display x25 map Interface: Serial2/0(protocol status is UP) ip 168.173.24.2 X.121 address:30561002 Map-type: SVC_MAP VC-number: 1 Facility: ip 168.173.24.3 X.121 address:30561003 Map-type: SVC_MAP VC-number: 1 Facility: