MST Notes

History Spanning Tree Protocol (STP) is a protocol to ensure there is no loop in layer 2 network. This protocol was invented by Radia Perlman in 1985 and published as a standard originally as IEEE 802.1D-1990. In essence, STP works by sending a probe to every layer 2 switches and decides which link should be…

IGMPv2 – RFC 2236

While PIM controls the communication between multicast routers, IGMP is the control protocol between routers and hosts. IGMP is similar with ICMP and it has IP protocol number 2. Because the intention is the communcation between hosts and routers, it is only sent as a link-local packet that has TTL of 1 in the IP…

PIM Sparse-Mode (SM) Notes – RFC 4601

Uses both Shared-Tree (*,G) and Source-Tree (S,G). PIM Sparse-Mode (SM) steps: Discover PIM neighbor and elect DR. PIM is the infrastructure to deliver the multicast packet. It builds the multicast network hop-by-hop. It takes the advantage of the routing table to perform RPF but it does not really matter what routing protocol derives it from….

Multicast: Overview

The way an IP packet delivered from server to client or vice versa is mostly known as unicast delivery. A server will need to know the client’s IP Address and assign this client’s IP address to the IP packet to be delivered. The more clients the server has, the more packets should be created and…

Cisco VIRL on VMware Fusion Notes

These are some notes to install Cisco VIRL version 0.9.17 (file virl.0.9.17.pc.ova) on VMware Fusion Professional Version 7.1.1 on MAC OSX Mavericks version 10.9.5. If you happen to hit this page, I’m sure you’re also having an issue with it. So, I thought I should write down some notes here.

Backpack for Network Engineer

I had been using Samsonite laptop backpack since 2008. It’s just this littleĀ problem that it does not have padding on its bottom corner on the laptop compartment. It’s not really a big deal, quite happy so far, until I dropped it exactly on the corner of it. See the photo below and you’ll know how…

Cisco IOS IPS

If you’re tasked to configure an Internet router, what features/services you would usually put in? You most definitely require NAT for LAN to Internet IP address translation, ACL for blocking unnecessary traffics from Internet to LAN, and might be a bit of router hardening by locking down some unnecessary services and management/control plane.

How to Fail CCIE Exam and Learn From It.

A note to myself. Time flies! It’s been a little more than a year since I wrote a post to my blog. Quite a few things happened in my life and priorities change. I decided to postpone my CCIE RS lab for sometime after several failed attempts. No, I’m not giving up yet, It’s just…

Router ACL on SVI; Inbound or Outbound?

Just a little note for SVI Access-List (or Cisco calls it Router ACL on SVI). Three routers configured as below. ! R1 int f0/0 ip addr 12.12.12.1 255.255.255.0 no shut router ospf 1 net 0.0.0.0 0.0.0.0 a 0 ! R2 int vlan 100 ip addr 12.12.12.2 255.255.255.0 int f1/0 switchport mode access switchport access vlan…