Serial Point-to-Point Overview

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To understand the Serial Point-to-Point Overview in a practical way, let’s break it down with a real-world scenario, topology, and simulation steps in GNS3.

Scenario Overview

In this example, we will simulate a simple point-to-point serial link between two routers. A serial connection typically uses a dedicated link between two routers, often used in WAN (Wide Area Network) connections. The serial link in this case will be used to connect two routers to communicate with each other.

Topology

Let’s create a simple topology:

• Router1 (R1)

• Router2 (R2)

• A serial link between R1 and R2

The interfaces used for the serial link will be Serial3/0 on both routers. The routers will use PPP (Point-to-Point Protocol) on the serial link to ensure communication.

Topology

Step-by-Step Guide

Step 1: Build the Topology in GNS3

1. Open GNS3 and create a new project.

2. Drag and drop two routers (e.g., Cisco 7200 or Cisco 2900 series) into the workspace.

3. Add a serial link between the two routers. Use Serial0/0/0 on both routers.

4. Connect the routers using a serial link (use a crossover cable or a serial cable between the interfaces).

Step 2: Configure Router Interfaces

• Access Router1 and enter the configuration mode:

R1#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#

• Configure the Serial Interface on Router1:

R1(config)#interface serial 3/0
R1(config-if)#ip address 192.168.1.1 255.255.255.252                                                                                       changed state to up
R1(config-if)#encapsulation ppp
R1(config-if)#no shutdown

• Access Router2 and enter the configuration mode:

R2#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#

• Configure the Serial Interface on Router2:

R2(config)#interface serial 3/0
R2(config-if)#ip address 192.168.1.2 255.255.255.252
R2(config-if)#encapsulation ppp
R2(config-if)#no shutdown

Step 3: Verify the Configuration

• Check the interface status on Router1:

R1#show ip interface brief
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            unassigned      YES unset  administratively down down
FastEthernet1/0            unassigned      YES unset  administratively down down
GigabitEthernet2/0         unassigned      YES unset  administratively down down
Serial3/0                  192.168.1.1     YES manual up                    up
Serial3/1                  unassigned      YES unset  administratively down down
Serial3/2                  unassigned      YES unset  administratively down down
Serial3/3                  unassigned      YES unset  administratively down down
Serial3/4                  unassigned      YES unset  administratively down down
Serial3/5                  unassigned      YES unset  administratively down down
Serial3/6                  unassigned      YES unset  administratively down down
Serial3/7                  unassigned      YES unset  administratively down down
R1#

Ensure the serial interface is up and has the correct IP address.

• Check the interface status on Router2:

R2#show ip interface brief
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            unassigned      YES unset  administratively down down
FastEthernet1/0            unassigned      YES unset  administratively down down
GigabitEthernet2/0         unassigned      YES unset  administratively down down
Serial3/0                  192.168.1.2     YES manual up                    up
Serial3/1                  unassigned      YES unset  administratively down down
Serial3/2                  unassigned      YES unset  administratively down down
Serial3/3                  unassigned      YES unset  administratively down down
Serial3/4                  unassigned      YES unset  administratively down down
Serial3/5                  unassigned      YES unset  administratively down down
Serial3/6                  unassigned      YES unset  administratively down down
Serial3/7                  unassigned      YES unset  administratively down down
R2#

• Testing Connectivity

R1#ping 192.168.1.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/21/32 ms
R1#

Optional: Adding Routing

You can also add a static route or configure routing protocols to enable communication between networks beyond just the serial link.

Example of static routing:

• On Router1:

R1(config)#ip route 0.0.0.0 0.0.0.0 192.168.1.2

• On Router2:

R2(config)#ip route 0.0.0.0 0.0.0.0 192.168.1.1

Keywords

Serial Point-to-Point, WAN connection, PPP encapsulation, Cisco CCNA, GNS3 simulation, serial interface, IP addressing, point-to-point link, router configuration, encapsulation protocol, troubleshooting serial links, show commands, static routing, subnet mask, network topology, serial cable, data encapsulation, ping test, routing protocols, Cisco routers, سیسکو