subnet mask and Boolean Algebra

binarysoul

I was reading a guide on CCNA mentioning subnet mask/boolean algebra.

Does anybody know how boolean algebra relate to subnet mask? I know boolean algebra, but I can't understand it's relation here:

"Working with subnet masks, you need only four basic principles of Boolean algebra:
· 1 and 1 = 1
· 1 and 0 = 0
· 0 and 1 = 0
· 0 and 0 = 0

The process of combining binary values with Boolean algebra is called anding. There are default standard subnet masks for Class A, B and C addresses. The commonly used subnet masks for each IP address class are:

Class A
255.0.0.0

Class B
255.255.0.0

Class C
255.255.255.0"

kevozz

Try this link.

For an easy explanation:

http://www.dummies.com/WileyCDA/DummiesArticle/id-2265.html

For a more in-depth explanation:

http://docsrv.sco.com/SM_nsm/subnet.htm

BubbaJ

binarysoul wrote:

The process of combining binary values with Boolean algebra is called anding. /quote]

There is a whole lot more to Boolean aglebra than anding. Simple high school Geometry has more than you need for subnetting, ACLs, etc.

Webmaster

Download our IP subnet calculator from www.techexams.net/ip-subnet-calculator than enter an IP, select a prefix/mask, and then when the network address, broadcast address, first host and last host address are displayed, click on the label "Network Address:". That will open a 'not-so-secret' dialog box showing the ANDing process for determining the network address based on the ip address and mask. This is what a network device uses to determine whether another IP (of a target host for example) is in the same IP subnet (which is the case if their network address is the same).

For learning how to calculate subnets, hosts etc I suggest going to www.learntosubnet.com

[mental note to self: add topics with subnetting info to CCNA FAQ topic...]

TheShadow

Definitely add your new calculator to the CCNA faq topic....

Danman32

ANDing is pretty much all you need to know about boolean algebra as it relates to subnets in my opinion. But it is boolean algebra never the less. Don't let the term stump you.

However, there's more to subnetting and breaking up IPs to nets, subnets and hosts than ANDing.

BubbaJ

Danman32 wrote:

ANDing is pretty much all you need to know about boolean algebra as it relates to subnets in my opinion.

That's probably true for the CCNA exam, but you can have more complex scenarios where you need to do things like OR and XOR.

EdTheLad

BubbaJ wrote:

Danman32 wrote:

ANDing is pretty much all you need to know about boolean algebra as it relates to subnets in my opinion.

That's probably true for the CCNA exam, but you can have more complex scenarios where you need to do things like OR and XOR.

I havent come across the need to XOR or OR, only ANDing so far when its come to subneting and using binary.Maybe with route-maps or class-maps i've had to OR,AND,NAND,XOR the commands logically, following a boolean logic,but anyone can do this without the knowledge of boolean.If this isnt what you mean please elaborate.

BubbaJ

ed_the_lad wrote:

I havent come across the need to XOR or OR, only ANDing so far when its come to subneting and using binary.Maybe with route-maps or class-maps i've had to OR,AND,NAND,XOR the commands logically, following a boolean logic,but anyone can do this without the knowledge of boolean.If this isnt what you mean please elaborate.

Well, you may need to use XOR to combine multiple subnets for an ACL. That will give you the wildcard mask.

There are lots of ways you may need to use different operators in configuring a router, but, as I said, high-school geometry will have more than prepared you for this.