BGP Issue: AS Number Mismatch
February 23, 2025 - Reading time: 2 minutes
When troubleshooting a BGP session that remains in the Idle or Active state, one of the most common issues is an incorrect configuration of the remote AS (Autonomous System) on one of the routers. In BGP, both peers must have matching AS numbers in their respective remote-as statements for the session to be successfully established.
BGP Verification
February 15, 2025 - Reading time: 3 minutes
In the previous lesson, we established iBGP peering between two routers in the same Autonomous System (AS 2350) and configured network advertisements.
Last Lesson's Summary:
- iBGP Peering Setup – We configured two routers (Router0 & Router1) to form an iBGP relationship.
- Network Advertisements – Router0 advertised 50.50.50.0/24 and 70.70.0.0/16 into BGP.
- Reachability Requirements – iBGP neighbors must be IP reachable before a BGP session can establish.
- Synchronization & Auto-Summary – The configuration assumes that synchronization is disabled and auto-summary is off to ensure proper route advertisement.
We ended the lesson with a challenge to verify iBGP was properly advertising routes and to advertise Loopback1 on both devices.
iBGP Introduction
February 5, 2025 - Reading time: 3 minutes
BGP (Border Gateway Protocol) is the backbone of the internet, enabling networks to communicate and exchange routing information. It allows routers to determine the best path for forwarding data between different networks, known as Autonomous Systems (ASes).
There are two types of BGP:
- eBGP (External BGP) – Used between different networks, like between two Internet providers or a company and its internet provider.
- iBGP (Internal BGP) – Used within the same network to keep routing consistent.
In this lesson, we’ll configure iBGP between two routers in the same Autonomous System (AS). Using AS 2350, Router0 will advertise the networks 50.50.50.0/24 and 70.70.0.0/16, and Router1 will receive these routes through the iBGP session and install them into its routing table.
Radius Server Configuration
July 17, 2024 - Reading time: 2 minutes
The previous tutorials covered the basics of AAA (Authentication, Authorization, and Accounting) in Cisco devices. It included an overview of how to configure local authentication, where user credentials are stored directly on each device. We also discussed the principles of using an external authentication server to centralize user credentials and authentication processes, laying the groundwork for a RADIUS server setup with PocketCLI. Understanding these concepts is crucial as we move forward to implementing RADIUS for centralized authentication.
Radius Server Setup
September 10, 2023 - Reading time: ~1 minute
In a Cisco environment, a RADIUS (Remote Authentication Dial-In User Service) server is commonly used to authenticate users for various network services, one of which is network access. This lab introduces using a RADIUS server to allows for centralized user authentication. Instead of maintaining separate user accounts and authentication databases on each network device. All authentication requests are sent to the RADIUS server. This centralization simplifies administration and ensures consistent authentication across the network.
AAA Authentication Using Local Credentials
February 25, 2023 - Reading time: 2 minutes
Cisco AAA (Authentication, Authorization, and Accounting) local authentication is a security feature that allows network administrators to control access to network devices and services by requiring users to provide valid credentials before accessing them. With local authentication, administrators can define user accounts and passwords locally on a network device, rather than relying on external authentication servers.
To configure Cisco AAA local authentication, follow these steps: