Configuring Multi-VLAN DHCP
March 25, 2025 - Reading time: 4 minutes
Dynamic Host Configuration Protocol (DHCP) allows a router to automatically assign IP addresses and other network parameters (such as default gateway and DNS server) to hosts. In a router-on-a-stick setup, one physical interface on the router is divided into multiple subinterfaces, each subinterface corresponding to a VLAN. The router will act as a DHCP server for each VLAN.
Password Recovery
March 11, 2025 - Reading time: 2 minutes
The Password Recovery procedure is used to regain administrative access to a device when passwords are lost or forgotten. This method involves interrupting the boot process to enter ROMMON mode, bypassing the startup configuration, and then resetting the necessary credentials. The recovery process requires precise use of configuration register changes to ensure the device boots properly without the previous settings. By following these steps, administrators can restore secure access while maintaining the integrity of the existing configuration.
BGP Troubleshooting
March 4, 2025 - Reading time: 2 minutes
Common Mistakes and How to Avoid Them
When configuring BGP, several common mistakes can cause session failures, missing routes, or improper route propagation. These mistakes can cause sessions to remain in Idle/Active states or prevent advertised routes from being installed in the routing table.
Below are the most frequent errors, their causes, and how to troubleshoot them effectively. To view a detailed explanation for each issue, simply click the provided links.
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.
