The First Honest Cable Company (comedy)

History of the Internet

ADSL Modulation

Ever wondered what “ADSL modulation” is? I love to explore or tinker routers and switches fresh out of the box.  I check the manual or sometimes go straight to its settings and view each tab to see its capabilities. One of the settings I usually come across is called ADSL modulation.

/31 : What kind of sorcery is this?!

A few years ago a friend asked me: "Does the /31 (255.255.255.254) subnet mask have a purpose and does anyone even use it?". 

VRF

Virtual Routing and Forwarding (VRF) allows  multiple "virtual routers" to exist within a single physical router. 

Think of it as  "VMWare for ROUTERS" where the physical router will maintain separate and instinct routing tables  for each "virtual router". This allows the physical router to store routes and forward packets even if the "virtual routers" are using identical addressing. 

Switchport Host: Two commands in one blow!

 
There's this "mabangis" Cisco IOS command that I discovered recently. It is the switchport host command and it automatically does three things:

1. Configures a switchport to access mode (for hosts)             
2. Enables portfast
3. Disables Etherchannel capabilities

Route Filtering with Distribute Lists

Routers running routing protocols send updates to indicate network reachability. At some point, you will have to filter those updates. Why? First,to hide certain networks from the rest of the organization. Second, to control network overhead on the wire. Cisco IOS provides many tools to control/filter routing updates and one of them is the Distribute List.