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Sunday, December 8, 2019

Three possible scenarios of Software Defined Networking (SDN)

Software-defined networking (SDN) is an approach to create a centrally controlled programmable packet network. Any protocols with the same approach could be considered as SDN as well.

For open protocols, we have one popular standard protocol “OpenFlow” talking among the central controllers to all managed networking devices. Open Network Foundation (ONF) defines OpenFlow protocol.

In fact, vendors also have developed proprietary protocols to implement this same approach. For example, Cisco’s ACI is a proprietary SDN solution.

Here I summarize 3 most probable scenarios when we deploy SDN.

Monday, November 18, 2019

Where do we use Cisco Wildcard Masks?

People might still be interested in about Cisco Wildcard Masks. I try to summarize interesting information about Wildcard Masks in this post.

Use Case 1: IPv4 Access Control Lists on Cisco IOS, IOS XE, and IOS XR


Wildcard masks are for us to select only subsets of IPv4 addresses.

Tuesday, November 5, 2019

Revised post: Covering Subnet Calculator to understand more about Wildcard Mask


This tool is an update to my previous post:
Simple visual tool to calculate Cisco IOS Wildcard Mask

Notes for Cisco IOS Wildcard Mask


You can simply assume Cisco IOS Wildcard Mask are derived by mapping 1s to 0s and 0s to 1s of equivalent subnet mask in binary notation.

Sunday, November 3, 2019

Global BGP IPv4 table is around 800K in size

This week the global BGP IPv4 table is around 800,000 entries in size. I bring this up just to give you a head-up and say a “Wow”. I don’t want to make you worry about the number. This is not my intention.

I still remember the “old good time” when I had installed a BGP router (Cisco 3660) with 256 Megabytes of DRAM memory in year 2001. At that time, the BGP table is below 150,000 entries so that router worked well.

Sunday, October 20, 2019

Scanning active IPv4 addresses is difficult? Simpler than you think

It is always a best practice to keep full track of all IP address assignments inside our local area network. From time to time, it might also be a good idea for security purposes to check whether we have any hidden nodes inside our network.

To discover any node with active IP addresses inside our network, we might imagine that we must acquire powerful tools such as Cisco Prime Infrastructure before we can achieve anything. In fact, it might be much easier than you have expected. Let me show you how.

All you must have is a Windows 10 PC. I think that should be easy.

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