VLSM & ROUTE SUMMARIZATION

KMAN24

Will VLSM and Route Summarization be on 640-801 ? Can anyone help with these topics ? I understand basic Subnetting well but have not dealt with VLSM. Should I prepare for these topics now or will they be covered more in higher level cisco exams.

Maybe a new TechNote from the Webmaster on These ?


Thanks in Advance

keenon

sybex ccna 4th edition does a good job explaining it.. but the summarization it touches it a lil but its covered more in bsci

wildfire

VLSM will certainly be covered in the exam! route summarisation gets touched upon but only a little bit.

Ten9t6

VLSM will be covered....even if RS is not covered as much on this exam, you will need to really know it to move on in your Cisco studies. After checking out the technotes on this site, check out www.howtosubnet.com . It used to have some good material.

Nocturnal

This stuff isn't that hard; you just have to drill yourself. Consider these points:

Regular classful

Class A 255.0.0.0 = /8
Class B 255.255.0.0 = /16
Class C 255.255.255.0 = /24

Know these numbers:

128,192,224,240,248,252,254,255 This is the progression of the decimal values of the byte as subnet bits are masked...notice that there are eight of them, one for each position in the byte.

128 1000 0000
192 1100 0000
224 1110 0000
240 1111 0000
248 1111 1000
252 1111 1100
254 1111 1110
255 1111 1111

So, if you have a /11, that's the same as a mask of 255.224.0.0;
a /19 has a mask of 255.255.224.0, and /27 is 255.255.255.224.

Other than zero, those are the ONLY decimal numbers you'll EVER see in a SUBNET mask...any other number is mathematically impossible. I emphasized subnet because this axiom does not apply to wildcard masks, which go in the opposite direction, but that's a different topic.

Hope this helps!!

Webmaster

Good post Nocturnal! I've started on Subnetting TechNotes using a similar approach, as in memorizing subnets instead of calculating them. The thing with subnetting in real-life is that you know it either by heart (when you got plenty of experience calculating them) or use a subnet calculator (when you occasionally have to calculate them). So for the exam, if you're having difficulty calculating subnets, you might as well memorize the answers upfront.

wildfire

what I do for exams is pretty mcu h straight after getting in there on the marker pad they give you I write them all down, it takes like 2 mins but saves on time later and you can just refer to it.