From: Faryar Zabihi \(fzabihi\) (fzabihi@cisco.com)
Date: Thu May 18 2006 - 14:18:29 ART
In your table you are describing 192.168.1.0/27
/24 would give you 254 host addrs.
192.168.1.0/25 192.168.1.0 network 192.168.1.127 broadcast
192.168.1.128 network 192.168.1.255 broadcast
192.168.1.0/26 192.168.1.0 network 192.168.1.63 broadcast
192.168.1.64 network 192.168.1.127 broadcast
And so on...
Not sure if this answers it or if I am reading what you are saying
correctly
Faryar
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Radioactive Frog
Sent: Thursday, May 18, 2006 11:47 AM
To: ccielab@groupstudy.com
Subject: Subneting - Basic Question but doubt full
Hi Guys,
Very basic question but lots of doubt.
1) First question:
If class C subnet 192.168.1.0 is routed to ISP-B (small) by ISP-A (BIG
ISP).
When ISP B starts subneting the 192.168.1.0 IP block for different
customer why do he starts distributing from the first subnet from
192.168.1.0/24 (which sholdn't be used)???????????
The books and theory says first and last subnet shouldn't be used (as
network and broadcast subnets), hence we shouldn't use the
192.168.1.0/24(first subnet)
Means the ISP should start distributing from second subnets e.g.
192.168.1.32 (see below).
---------------------------------------------------------
Subnet , Valid Hosts , Broadcast
192.168.1.0 , 192.168.1.1 to 192.168.1.30 , 192.168.1.31
192.168.1.32 , 192.168.1.33 to 192.168.1.62 , 192.168.1.63
192.168.1.64 , 192.168.1.65 to 192.168.1.94 , 192.168.1.95
192.168.1.96 , 192.168.1.97 to 192.168.1.126 , 192.168.1.127
192.168.1.128 , 192.168.1.129 to 192.168.1.158 , 192.168.1.159
192.168.1.160 , 192.168.1.161 to 192.168.1.190 , 192.168.1.191
192.168.1.192 , 192.168.1.193 to 192.168.1.222 , 192.168.1.223
192.168.1.224 , 192.168.1.225 to 192.168.1.254 , 192.168.1.255
1) Second question:
What if ISP starts distributing /25 /26 /27 IP blocks from
192.168.1.0/24 IP block to the customers ? In this case what subnet mask
shouldn't be used (still first and the last in 192.168.1.0/24 blocks) ?
Appreciate your answers to this basic topic!
Frog!
This archive was generated by hypermail 2.1.4 : Thu Jun 01 2006 - 06:33:21 ART