how to configured two routers extened standard ACL LIST with serial cable commands prompt 2026
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How to Configure Two Routers Using Extended Standard ACL with Serial Cable (Command Prompt Guide 2026)
URL: https://sreekrishnatechsolutionsatp2026.blogspot.com/
Author Contact: pgollabala@gmail.com
Introduction
In modern networking, security and traffic control are critical components for efficient communication between devices. One of the most powerful tools available in router configuration is the Access Control List (ACL). This guide explains how to configure two routers using an extended ACL over a serial cable connection, using command-line interface (CLI) methods.
This tutorial is designed for beginners and intermediate learners preparing for networking exams or working on real-world configurations. It also follows SEO best practices to help rank on Google’s first page and supports AdSense approval requirements.
What is an ACL?
An Access Control List (ACL) is a set of rules used by routers to filter network traffic. ACLs determine which packets are allowed or denied based on criteria such as:
Source IP address
Destination IP address
Protocol (TCP, UDP, ICMP)
Port numbers
Types of ACLs
Standard ACL
Filters based only on source IP address
Extended ACL
Filters based on source, destination, protocol, and ports
More powerful and flexible
Network Topology
In this setup, we use:
Router 1 (R1)
Router 2 (R2)
Serial cable connection between routers
Two LAN networks connected to each router
Example IP Scheme
| Device | Interface | IP Address |
|---|---|---|
| R1 | G0/0 | 192.168.1.1/24 |
| R1 | S0/0/0 | 10.0.0.1/30 |
| R2 | G0/0 | 192.168.2.1/24 |
| R2 | S0/0/0 | 10.0.0.2/30 |
Step 1: Basic Router Configuration
Configure Router 1
enable
configure terminal
hostname R1
interface g0/0
ip address 192.168.1.1 255.255.255.0
no shutdown
interface s0/0/0
ip address 10.0.0.1 255.255.255.252
clock rate 64000
no shutdown
exit
Configure Router 2
enable
configure terminal
hostname R2
interface g0/0
ip address 192.168.2.1 255.255.255.0
no shutdown
interface s0/0/0
ip address 10.0.0.2 255.255.255.252
no shutdown
exit
Step 2: Configure Routing
To enable communication between networks, configure static routing.
On Router 1
ip route 192.168.2.0 255.255.255.0 10.0.0.2
On Router 2
ip route 192.168.1.0 255.255.255.0 10.0.0.1
Step 3: Configure Extended ACL
Extended ACLs should be placed close to the source of traffic.
Scenario
Allow only HTTP traffic from Network 1 to Network 2
Deny all other traffic
On Router 1
access-list 100 permit tcp 192.168.1.0 0.0.0.255 192.168.2.0 0.0.0.255 eq 80
access-list 100 deny ip any any
Step 4: Apply ACL to Interface
Apply the ACL to the outgoing interface toward Router 2.
interface s0/0/0
ip access-group 100 out
exit
Step 5: Verification Commands
Use the following commands to verify configuration:
show access-lists
show ip interface
show running-config
Test connectivity using:
ping 192.168.2.1
Troubleshooting Tips
Ensure interfaces are up/up
Verify IP addressing and subnet masks
Check routing table using:
show ip routeConfirm ACL placement and direction
Common Mistakes to Avoid
Applying ACL in wrong direction (in/out)
Using incorrect wildcard masks
Forgetting “no shutdown” command
Misplacing extended ACL (should be near source)
Advantages of Extended ACL
Granular control over network traffic
Enhanced security
Ability to filter specific applications
Better bandwidth management
Conclusion
Configuring two routers using an extended ACL over a serial connection is a fundamental networking skill. By following this guide, you can:
Establish router-to-router communication
Implement traffic filtering using extended ACL
Improve network security and performance
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FAQs
What is the difference between standard and extended ACL?
Standard ACL filters only source IP, while extended ACL filters source, destination, protocol, and ports.
Where should extended ACL be placed?
Near the source of traffic.
Why use serial cable in routers?
It is used for WAN connections between routers in labs and real-world scenarios.
Author: Sree Krishna Tech Solutions
Contact: pgollabala@gmail.com
Website: https://sreekrishnatechsolutionsatp2026.blogspot.com/