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 lets switches negotiate trunk formation automatically—but this convenience comes with security risks that make disabling it a best practice in production networks.
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.
VLANs are more than a configuration checkbox — they change how every frame is tagged, forwarded, and filtered inside the switch. Here's the mechanics.
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 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 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 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.
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.
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.
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.
BGP confederations scale iBGP by dividing the AS into sub-ASes that speak confederation eBGP internally, while appearing as a single AS to the outside world. An alternative to route reflectors with tradeoffs you need to know.