How to work with VLSM in the Cisco CCNA -Part1

http://danscourses.com - A tutorial on VLSM Variable Length Subnet Masks in the Cisco CCNA
http://www.danscourses.com

Category:

Education

Tags:

• VLSM
• Cisco
• CCNA
• 'Variable
• Length
• Subnet
• Masks'

[sagetajr]

But /27 isnt enough it only gives 6 usable nets out of 8 subnets : 8 subnets - 2(net/broadcast)= 6 .....wouldnt a /28 be used instead? which will give out 14 usable subnets out of 16 subnets : 16 subnets - 2(net/broadcast)= 14....

[danscourses]

@sagetajr only on the older IOS' could you not use the first and last subnets with the newer versions of the Cisco IOS you can use all of the subnets.

[sagetajr]

can i use 192.168.12.0 ?

would that have the same /27 sub-net mask or no?

[danscourses]

@sagetajr Yes you can start with 192.168.12.0 but if you need to divide it up into separate subnets then yes you need to come up with a plan for dividing the networks into smaller groups. If you used a /27 on every subnet that would make 8 subnetworks 192.168.12.0, 192.168.12.32, 192.168.12.0, 192.168.12.64, 192.168.12.96, 192.168.12.128, 192.168.12.160, 192.168.12.192, and 192.168.12.224,

[danscourses]

@sagetajr Yes you can start with 192.168.12.0 but if you need to divide it up into separate subnets then yes you need to come up with a plan for dividing the networks into smaller groups. If you used a slash 27 on every subnet that would make 8 subnetworks 192.168.12.0, 192.168.12.32, 192.168.12.0, 192.168.12.64, 192.168.12.96, 192.168.12.128, 192.168.12.160, 192.168.12.192, and 192.168.12.224,

[TheDynamix10]

You cant use the 192.168.1.1 network more than once lol

[danscourses]

@TheDynamix10

I think you mean you can't use the 192.168.1.1 host number more than once, but absolutely, you can divide the 192.168.1.0 network into multiple subnets. That "is" subnetting.

[openyada]

@sagetajr that's for the number of hosts is each subnet you check how many host bit you have and here if you borrow 3 bits you have 5 host bits left, so in each subnet you have 2 to the power 5 which is 32. you take the broadcast and network addresses away. which leave you with 30 usuable addresses in each subnet

[MrWxoxw]

Thanks dear, my respect

[zevendonk2300]

Thanks for you're tutorials. This video's about subnetting made me clear about how it's done. My exam went VERY well thanks to you're skill to teach people. thanks and regards from Belgium :D

[TheJonredfern]

very well explained; along with part 2 makes perfect sense

[SeanYves09]

@danscourses Wait a minute, /27 gives you 16 possible networks not 8 soo....

[sagetajr]

@danscourses

oh man thanks for the update.. i did not know that

[IKnowALittleCuban]

I agree with onrajeev, there are 30 hosts/network. You can't count network and broadcast addresses.