Thursday, November 20, 2014

A simple example explaining why we need Prefix-List in addition to simple Access-List (ACL) on Cisco IOS

My example is: assume we want to filter out "all possible subnets/prefixes inside 192.168.1.0/24" from rushing into our router.

Red House Theater, at the West Gate of Taipei Wall (西門紅樓、紅樓劇場). 
We can first visualize what subnets are to be filtered in the following, but incomplete list:
192.168.1.0/24

192.168.1.0/25
192.168.1.128/25

192.168.1.0/26
192.168.1.64/26
192.168.1.128/26
192.168.1.192/26

(and even more ...)

Wednesday, November 19, 2014

RFC 3021: the "/31" subnets for IPv4 Point-to-point Links

(This RFC has been there for almost 14 years. Without writing a post down about it, it would never stay in my mind as if I have never known it. Too bad for me!)

Original location of West Gate of Taipei City Walls (西門、西門町).
The gate and the walls were removed long time ago.
The bottom right is one of the entrance of  MRT Ximen (e.g. West Gate) Station.

RFC 3021: Using 31-Bit Prefixes on IPv4 Point-to-Point Links

Since this RFC is quite old, almost all of today's routers already have this feature. It is very safe today to assign "/31" subnets to any point-to-point links. We can now save 50% of IPv4 addresses for point-to-point WAN links.

Thursday, September 11, 2014

New product: Cisco UCS "Mini"

Cisco has a new update few days ago to her Unified Computing System (UCS): the UCS Mini. Here is what I have known of it from the public web sites.

Sun is rising at Hualian County of Taiwan on August 30, 2014.

Tuesday, July 15, 2014

Cisco Exam costs "upgraded" on June 2014

Cisco upgraded her exam costs on June 2014. Basically, USD $50 is added to every exam.

This is already an old news. I just want to record it here in case you missed it.

[Original Post]
https://learningnetwork.cisco.com/docs/DOC-12825

[The following content is captured on Cisco.com.]
>>>

Last Modified:  Jun 20, 2014 2:57 PM by Madhukar: Cisco Team

What Do Exams Cost?

Computer-based certification exam (Written Exam) prices range depending on scope and exam length. Please refer to the table below.

sPATHENTRYASSOCIATEPROFESSIONALEXPERTSPECIALIST

Cost$125 - $150$150 - $295$250$400$250

  • CCIE Lab and CCDE Practical exams are $1,600 USD per attempt at permanent Lab Locations.   Information on Mobile CCIE labs can be found here. Travel and lodging expenses are the responsibility of the candidate and are not included in the exam price.
  • Expert and Architect level Lab and Practical exam information links: CCIE Lab Exams , CCDE Practical Exams and CCAr.
  • Costs may vary due to exchange rates and local taxes (VAT, GST).
  • Register online at Pearson VUE for all exams except CCIE Lab exams. Payment is made directly to the authorized test delivery partner, Pearson VUE.
  • You are responsible for any fees your financial institution charges to complete the payment transaction. Payment is made online via credit card or wire transfer. Price is not confirmed and subject to change until full payment is made.
  • For exact pricing of your exam please register online at Pearson VUE. Exams prices vary depending on scope and exam length.

Saturday, June 21, 2014

Threatening the market by “Wedge”? I don't think so.

A grass next to Taipei Botanical Garden (台北植物園), Taiwan
I just don't get it. Products such as iPhone/iPad are totally proprietary. And people still love them. Network devices are also proprietary. However, people just don't like proprietary network boxes and want them all to become as open as commodities?

Last Wednesday (June 18, 2014) Facebook announced the existence of their experimental in-house Top of Rack 40Gbps switch called “Wedge”. The basic ideas in many reports from the press (like this, this, and this) are: this would threaten existing market of network vendors such as Cisco.

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