Inter-VLAN Routing on a Layer 3 Switch: SVI-Based Routing on Catalyst 9000
Layer 3 switches route between VLANs in hardware at wire speed — no external router bottleneck. Here is how to configure SVI-based inter-VLAN routing on a Catalyst 9300.
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Latest posts — page 47
Inter-VLAN Routing with Router-on-a-Stick on Cisco IOS XE
When you don't have a Layer 3 switch, router-on-a-stick provides inter-VLAN routing via a single physical link split into subinterfaces. Learn when this design is appropriate, how to configure subinterfaces, and why it's a bandwidth bottleneck.
DTP (Dynamic Trunking Protocol): How It Works and Why You Should Disable It
DTP lets switches negotiate trunk formation automatically—but this convenience comes with security risks that make disabling it a best practice in production networks.
VLAN Access Ports and Switchport Modes: Access, Trunk, and Dynamic
Learn the differences between access mode, trunk mode, and dynamic trunking protocol negotiation on Cisco Catalyst switches, and why static configuration is the production standard.
How VLANs Work: Tagging, Broadcast Domains, and Frame Forwarding
VLANs are more than a configuration checkbox — they change how every frame is tagged, forwarded, and filtered inside the switch. Here's the mechanics.
What Is a VLAN? Virtual LANs Explained for Network Engineers
VLANs let you carve one physical switch into multiple isolated broadcast domains — without buying more hardware. Here's how they work and why every network uses them.
BGP Path Attributes Explained: Well-Known vs Optional
BGP path attributes are the foundation of every traffic engineering technique: local preference, MED, AS-path prepending, communities. Understand the well-known vs optional attribute matrix before touching policy.
BGP Message Types: OPEN, UPDATE, KEEPALIVE, and NOTIFICATION
BGP uses just four message types: OPEN, UPDATE, KEEPALIVE, and NOTIFICATION. Understanding the field-level format of each makes debug output and packet captures far more readable for anyone troubleshooting BGP.
eBGP vs iBGP: What's the Difference and When to Use Each
eBGP and iBGP look similar at a glance but behave very differently around TTL, next-hop, AS-path, and route advertisement. Treating them as the same protocol gets you in trouble fast; here are the rules.
How BGP Works: Peers, Updates, and the Finite State Machine
BGP peering does not auto-discover. Every session is deliberately configured, runs over TCP port 179, and walks a strict finite state machine before a single route flows. The foundation you need before touching BGP config.
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What Is BGP? The Protocol That Runs the Internet
Every time you load a webpage, your traffic crosses networks owned by different organizations. BGP, the Border Gateway Protocol, is what stitches 75,000+ autonomous systems into a single working internet. Here is how, and why.
BGP Route Filtering with Prefix Lists
Prefix lists are the preferred BGP filtering tool: faster than ACLs, easier to read, and built for matching networks with specific prefix lengths. Every production BGP deployment needs them on inbound and outbound.