1. The command is "ip subnet-zero". It is a global config command, and can
be enabled on any router. This is generally not advised, due to inherent
confusion between subnet and network addresses.
2. Starting with the block 216.73.203.0/24, reserve 2 bits from the host
portion, this will give you 2 new subnets (ignoring the all zeroes, and all
ones) - 216.73.203.64/26, and 216.73.203.128/26.
Repeat the same process, again using 2 bits from the host portion (you can
use 1 bit if you like). The block, 216.73.203.64/26 will yield the subnets -
216.73.203.80/28 and 216.73.203.96/28. The other block, 216.73.203.128/26
will yield the subnets - 216.73.203.144/28 and 216.73.203.160/28. Repeat the
same process to get /30 subnets.
Please note that you can use any number of bits, and you can also use the
first and last subnets of all subsequent blocks. Do not use the first subnet
(all zeroes) of the main block (216.73.203.0), for the issue already pointed
out.
Hope this helps.
CM
-Original Message-
From: Oletu Hosea Godswill, CCNA.
To: Charles Manafa
Sent: 19/06/01 09:31
Subject: Re: Please Help with VLSM [7:9024]
Thanks a lot Charles,
I did understand your point, however two key questions are really
begging
for your answer:
1. How and where do I enable network zero (is it on the Core Routers,
Distribution Routers or
the Access layer Router)?
2. How do I carry out the further sudnetting from a reserved bit as you
explained in the second
paragraph of your email?
Regards.
Oletu
- Original Message -
From: "Charles Manafa"
To:
Sent: Tuesday, June 19, 2001 11:06 AM
Subject: RE: Please Help with VLSM [7:9024]
> I believe you can do that, if you enable subnet zero, and there won't
be
any
> address conflict because the subnet masks are different. But, you will
not
> get the number of subnets and hosts that you have specified. This is
because
> each time you subnet, you use up one address from the block you are
> subnetting from - hierachical thing.
>
> I would personally reserve bits from the assigned prefix block, and
use
> those reserved addresses for further subnetting. That way you will not
get
> into the pitfall where a network address is also a host address.
>
> CM
>
>
> -Original Message-
> From: Oletu Hosea Godswill, CCNA.
> To: [EMAIL PROTECTED]
> Sent: 19/06/01 07:52
> Subject: Please Help with VLSM [7:9024]
>
> Hi group,
>
> Please just throw more light of this. If I have a block of ip address,
> can I
> use different subnets for different purposes like this:
>
> If my block is 216.73.203.0
>
> 1. 216.73.203.0/26 4 Networks, 64 Hosts each
> 2. 216.73.203.0/27 -- 8 Networks, 32 Hosts each
> 3. 216.73.203.0/28 -- 16 Networks, 16 Hosts each
> 4. 216.73.203.0/29 -- 32 Networks, 8 Hosts each
> 5. 216.73.203.0/30 -- 64 Networks, 4 Hosts each.
>
> My desire is to use the item 5 for all my WAN links since it only have
2
> valid
> hosts per network and the rest for other purposes.
>
> But my problem is if I have use two same IP-addresses but from
different
> networks (eg one from item 3 and the other from item 4 above) assigned
> to two
> different hosts on both ends of a routable network, wouldn't the
system
> response with a conflict/duplication of IP-addresses or give some
other
> kind
> of error?
> Eg If, I have this scenerio:
>
> Host A = 216.73.203.21 255.255.255.248 (ie a host on network
> 216.73.203.16/29)
> Host B = 216.73.203.21 255.255.255.252 (ie another host on network
> 216.73.203.20/30)
>
> Questions:
> Since both hosts are on both sides of a routable network:
> 1. Wouldn't there be an IP-address conflict?
> 2. Wouldn't it be a duplication of IP-address?
> 3. If I ping 216.72.207.21, which of the two host will reply?
>
> OR
> 4. Is it that I can only variably subnet a block of IP-addresses once,
> say
> /29
> and use only hosts from that subnet and cannot do another subnetting
on
> that
> same block when the need arises?
>
> These are my questions.
>
> How I wish someone can clear this, for it will help myself and many
> other
> people in the group.
>
> Rgards.
> Oletu
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