| Author |
Dont get this one!!!!
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| JPL333 2002-03-06, 4:46 am |
| subnet mask 255.255.255.240
How many hosts can 10.0.0.0 have per subnet?
This should be easy for me but i got the answer very wrong. I must be missing a couple of steps....
Strike attack dont suppose you got any notes on this one?
As always any help is greatly appreciated | |
| hintgy 2002-03-06, 8:04 am |
| Let me see if can get this.
240 means you have taken 4 bits from the octet for subnetting and you have 4 bits remaining for hosts. So 2^4=16 minus 2 (1 for network address and 1 for broadcast address) equals 14 hosts.
This is easy (not CCIE level)! | |
| dmaftei 2002-03-06, 9:03 am |
| quote:
Originally posted by hintgy
... you have taken 4 bits from the octet for subnetting ...
Yeah, except that when you subnet 10.0.0.0 with 255.255.255.240 the "octet for subnetting" is the second octet plus the third octet plus the fourth octet. And while you DO get 14 hosts per subnet, you get 1048576 (2^20) subnets. | |
| darthfeces 2002-03-06, 9:11 am |
| yes,
but there are much more scalable solutions,
such as using 172.16-31.0.0 networks or even
192.168.255.255 net with this mask.
cisco has some design info somewhere ?
i can't remember
about layering address
assignments accross core-dist-access layers. | |
| Yeti-GBR1 2002-03-06, 9:21 am |
| darthfeces you have completely lost me on this one now...what are you on about? I know in the scheme of Cisco evolution I'm stull in the sludge, but what the devil does what you posted mean?
BTW I agree with dmaftei on the subnets & hosts  | |
| darthfeces 2002-03-06, 9:26 am |
| i was just commenting
that the network and mask will work,
but having 1 million subnets is an extremely
bad design idea.
you would be better off (and implementing a more scalable solution) by applying that mask to any of the 172.16-31.255.255 or
192.168.255.255 networks availible for internal use. | |
| dmaftei 2002-03-06, 10:12 am |
| quote:
Originally posted by darthfeces
having 1 million subnets is an extremely bad design idea.
OTOH you can think of it as challenging...  | |
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| JPL333 2002-03-06, 10:28 am |
| question 2 in the mini test (sorry) | |
| dmaftei 2002-03-06, 10:35 am |
| quote:
Originally posted by JPL333
question 2 in the mini test (sorry)
All those choices are wrong. If the other questions are the same quality you're better off forgetting about these guys...
The explanation is correct, but the mask used there (255.255.248.0) is different from the mask used in the question (255.255.255.240). Sloppiness... | |
| JPL333 2002-03-06, 10:41 am |
| Awesome,
Glad thats cleared up my confusion cheers guys....and girls | |
| hintgy 2002-03-07, 1:51 am |
| dmaftei wrote:
Yeah, except that when you subnet 10.0.0.0 with 255.255.255.240 the "octet for subnetting" is the second octet plus the third octet plus the fourth octet. And while you DO get 14 hosts per subnet, you get 1048576 (2^20) subnets.
Absolutely right. I was just answering the original post that asked about the number of hosts and not the number of subnets. Sorry for nitpicking here but in IMHO when you train for CCIE lab you have to learn to answer only the question asked. | |
| chodan 2002-03-07, 8:37 pm |
| quote:
Originally posted by hintgy
dmaftei wrote:
Yeah, except that when you subnet 10.0.0.0 with 255.255.255.240 the "octet for subnetting" is the second octet plus the third octet plus the fourth octet. And while you DO get 14 hosts per subnet, you get 1048576 (2^20) subnets.
Absolutely right. I was just answering the original post that asked about the number of hosts and not the number of subnets. Sorry for nitpicking here but in IMHO when you train for CCIE lab you have to learn to answer only the question asked.
The idea that the second octet is for subnetting has to be thrown out when the Subnet mask wanders outside classful boundaries.
Class based ip addressing is a legacy concept if you ask me, "and of course no-one will" It is mainly used as a logical marker
or frame of reference these days.
With VLSM and CIDR where mark network boundaries is up to you and your isp if they are public address space.
"now I`m the nit picker" |
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