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Wednesday, March 29, 2017

Clear configured allowed VSAN list on trunk ports of Cisco MDS

A friend asked a good question about how this command works on Cisco MDS FibreChannel switch: “switchport trunk allowed vsan all”.

To my surprise, I cannot find any specific official documents to explain it clearly. I did some experiment on one Cisco MDS 9148. And here is my conclusion.

Bay, beach, and cliff near Chung-De Station. (崇德海灣).
Hualian County, Taiwan.


Thursday, March 23, 2017

Cisco IOS/IOS XE Vulnerabiliy announced. Disable TELNET fast

This is just a short notice for you in case you are not aware of it. Cisco announced a vulnerability on Cisco IOS and IOS XE operating system. For short, you only have to disable incoming TELNET service onto the router itself to avoid this vulnerability. You can use Secure Shell (SSH) instead for remote management. SSH is not vulnerable in this problem.

The Jin-Dai Bridge (錦帶橋) in Dahu Park (大湖公園).
Taipei City, Taiwan.

Wednesday, August 24, 2016

Do more with “the same”

To emphasis the effectiveness of a new tool, we always hear some people say it would make you “do more with less”. This is so attractive to Chief Officers. How would the other staffs think about this?

Dongshan River Water Park (冬山河親水公園).
The venue of  Yilan International Children's Folklore and Folkgame Festival (YICFFF, 宜蘭國際童玩藝術節). Yilan County, Taiwan. 

The problem of “do more with less”

With the word “less”, what does that mean? Does that imply we don’t need that much budgets anymore? Does that imply we don’t need more hardware? Does that imply the workforce would be cut down?

Wednesday, May 18, 2016

CCNA v3 Exam is cheaper than v2

I create this post just to remind you in case you did not notice it yet.

Shihmen Dam (石門水庫), Taoyuan City, Taiwan.  (Wikipedia)

Version 3 Exam costs $250

CCNA Routing Switching Version 3 exam cost is now US$ 250. This is a good news because in v2 the exam cost was US$ 295. That is, the new exam is US$ 45 less than before.

This is great! Isn’t it!

Thursday, March 3, 2016

Diffie and Hellman Receive Turing Award 2015

When we study IPSec, we know Mr. Diffie and Mr. Hellman invented a method in year 1976 that is the core of Internet Key Exchange (IKE) to create mutually shared secret. We also have to specify and configure DH Group Number in ISAKMP policy sets (crypto-map in Cisco IOS).

A.M. Turing Award Logo. Captured on ACM Official Website.

I am not going to dig in the details about the mathematics behind Diffie-Hellman method. I just want you to know Mr. Diffie and Mr. Hellman receive Turing Award 2015 together.

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