First of all, may I welcome you to my site. My name is Chris and I'm from the UK and work as a Systems Engineer for Cisco. This blog was initially created to post up my subnetting technique but has now got more stuff to do with attaining Cisco certifications. Either way I really hope that the content is sufficent for your needs and I look forward to hearing your feedback. If you find that the content really helps you please feel free to donate using the PayPal link on the right.

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VLAN Trunking - Remembering which combination creates a Trunk Link

Ah, you've probably seen the table and thought to yourself "that doesn't look bad." Well let's make it easier:

1. If one end of the link is configured as an access port then the link will NOT trunk.
2. If BOTH ends of the link are AUTO then the link will NOT trunk
3. If one end is a trunk and the other is auto BUT THE TRUNK PORT IS CONFIGURED FOR NO-NEGOTIATION then the link will NOT trunk.

Posted byChris Bloomfield at 14:37  


sajay said... 4 August 2008 at 16:50  

hi chris,thank you u realy made subnetting easy,now i got a question,how to find cidr for an particular ip.

Chris Bloomfield said... 4 August 2008 at 18:24  

Hi Sajay,

First of all I'm glad that my technique has proved useful to you.

Unfortunately I'm not sure quite what you mean about finding CIDR for a particular IP. Can you please provide an example?

sandy said... 31 August 2008 at 11:16  

well sir can u please tell the cocept of vlsm

damodar said... 29 March 2010 at 12:42  

Hi chris
I am new to CCNA and jsut doing CCNA1 . Therefore i dont have any idea about Subnetting and supernatting which i found the most important.
And i went through your subnetting technique which is pretty simple and easy way to understand.It has been really very useful for me.
I have some questions and have excepted you will help me solving all these questions.If possible please mail me the solutions at my email address sharma.damodar1@gmail.com

An organization is assigned the network number, and it must create a set of subnets that supports up to 90 hosts on each subnet. Please answer the following questions:

1.1 Define subnet mask (or extended prefix length) for this organization .

1.2 Write IP number for the Subnet number 421 explicitly in binary and decimal notation ( Note: The first subnet starts from zero) .

1.3 Write explicitly IP address of the host number 68 on the Subnet number 421 .

1.4 What is the broadcast address for the Subnet number 421?

Question 2:
The following is a dump of a TCP header in hexadecimal format:
00CD0018 00000EF1 00000D5D 502200D1 01BF0010

Please answer the following two parts of questions:

2.1 What is the source port number?

2.2 What is the destination port number?

2.3 What is the sequence number?

2.4 What is the acknowledgment number?

2.5 What is the length of the header?

2.6 Which control bits are set? And what do they represent?

2.7 What is the window size?

2.8 What does the last four digits ‘0010' of the above dump represent? What action will the destination node take when it receives this packet?

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