dslreports logo
site
 
    All Forums Hot Topics Gallery
spc

spacer




how-to block ads


Search Topic:
uniqs
359
share rss forum feed

JDmailNY

join:2007-12-02
Pearl River, NY

[CCNA] Subnetting Class B please help first and last subnet

Having problems calculating what the Second host ?? ????? and Second to last host ????? for class B subnetting should be.

Subnet 0.0 128.0

First host 0.1 128.1

Second host ?? ?????

Second to last host ?????

Last host 127.254 255.254

Broadcast 127.255 255.255

HELLFIRE
Premium
join:2009-11-25
kudos:19
You [u]DO[/u] know we're not the Subnetting Homework Hotline, right JDmailNY See Profile ?

Secondly I question the relationship between these two figures

Subnet 0.0 128.0
 
First host 0.1 128.1
 

to each other, and their relationship to the 127.x.x.x range you're mentioning...

Regards


tubbynet
reminds me of the danse russe
Premium,MVM
join:2008-01-16
Chandler, AZ
kudos:1
they're awesome wildcard masks, HELLFIRE See Profile.

come on, think outside the box ;-P

q.

Network Guy
Premium
join:2000-08-25
New York
kudos:2
Reviews:
·Verizon FiOS
·Future Nine Corp..
·T-Mobile US
reply to JDmailNY
said by JDmailNY:

Having problems calculating what the Second host ?? ????? and Second to last host ????? for class B subnetting should be.

Subnet 0.0 128.0

First host 0.1 128.1

Second host ?? ?????

Second to last host ?????

Last host 127.254 255.254

Broadcast 127.255 255.255

Even if I were to interpret that based on class B addressing; and based on last host and broadcast; to be 25-bit subnet where for example:

191.255.127.254 = last host
191.255.127.255 = broadcast

That would still be:

191.255.126.1 = first host
191.255.127.253 = second to last host

So that question; as given to you; makes no sense without more detail.


Da Geek Kid

join:2003-10-11
::1
kudos:1
reply to JDmailNY
Please learn what it means subnetting. 127.0.0.0 is not a Class B and hence you are not to subnet Class B. It's a Class A which you require a 16bit subnet mask or a 16 bit subnetting NOT class B.

cramer
Premium
join:2007-04-10
Raleigh, NC
kudos:9
Actual /8 (class A) is 24 bits ( 8 + 24 == 32 ) And 127/8 is a special network -- per spec (rfc) it is "local host only" and never to be attached to a real interface, no packet should ever leave a system with such an address.

Yes, there have been documentation hacks (see Netopia re: dial profiles) but any modern OS that follows the rules won't let you "subnet" localhost:
rtr3745(config-if)#int f0/0                                       
rtr3745(config-if)#ip address 127.255.1.1 255.255.255.0 secondary 
Not a valid host address - 127.255.1.1