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Re: quick question?
- From: Howard C. Berkowitz
- Date: Thu Sep 17 11:44:50 1998
At 9:42 PM -0600 9/16/98, Kyle D. Smith wrote:
>First of all, i know that this is not the best place to ask this quesiton,
>but it is the only place that can quickly come to mind...
>I have a customer who has a block of 62 ip addresses (188.8.131.52 ->
>184.108.40.206 and one for network/brodcast). They are current expanding
>their network, and need around 30 more ip addresses. I went ahead and
>allocated them the following IP address pool (220.127.116.11 ->
>18.104.22.168 with network/brodcast address.) I attempted to use the new
>address on a Apple Macintosh (PowerMac 6500/75) and it erturned an error
>message saying that the router was not on the subnet, and that it could
>not use the new address. I know I should remember how to fix that, but I
>am not sure what to do.... Any help or guidence would be greatly
>appreciated. Thank you very much.
For a quick reference, download ftp://ftp.isi.edu/in-notes/rfc1878.txt
This will give you some templates for VLSM subnets. Here are some relevant
255.255.255.192 4 nets N.N.N.0 N.N.N.1-62 N.N.N.63
2 bit Class C 62 N.N.N.64 N.N.N.65-126 N.N.N.127
10 bit Class B N.N.N.128 N.N.N.129-190 N.N.N.191
N.N.N.192 N.N.N.193-254 N.N.N.255
255.255.255.224 8 nets N.N.N.0 N.N.N.1-30 N.N.N.31
3 bit Class C 30 N.N.N.32 N.N.N.33-62 N.N.N.63
11 bit Class B N.N.N.64 N.N.N.65-94 N.N.N.95
N.N.N.96 N.N.N.97-126 N.N.N.127
N.N.N.128 N.N.N.129-158 N.N.N.159
N.N.N.160 N.N.N.161-190 N.N.N.191
N.N.N.192 N.N.N.193-222 N.N.N.223
N.N.N.224 N.N.N.225-254 N.N.N.255
As you see, the first block you assigned is fully in the third /26 range.
The second block, starting with 144, is off somehow. I am a little unclear
if you wanted to give them a /26 or /27 block.
In addition, you need to make sure your router interface is visible on
both subnets. I'm assuming your configuration is something like this:
with the Macs addressed either in 22.214.171.124
The router interface needs to have an address in both subnets. On Cisco,
this is a secondary address, while on Bay, it would be a multinet addresss.
Strategically, encourage your customer to use DHCP address assignment. If
he does this, you can create a single block on the DHCP server for his
future address needs, and the workstations simply need to reboot to get new
As a shameless commercial plug, I have a book on addressing coming out in
November from Macmillan.