Date: Tue, 9 Jan 2001 18:09:24 -0500 From: "Troy Settle" <troy@psknet.com> To: "Colin Campbell" <sgcccdc@citec.qld.gov.au> Cc: <freebsd-isp@freebsd.org> Subject: RE: Hosting with multiple subnets Message-ID: <BFEGKDHLHDNOJEIHJDBACEOHCAAA.troy@psknet.com> In-Reply-To: <Pine.BSF.4.21.0101100831260.57827-100000@guru.citec.qld.gov.au>
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Colin,
I'm breaking netiqet by copying this back to the list, but I think that many
folks will find this useful or even educational.
You are correct, in that on a /26 subnet, you only have 62 usable IP
addresses, however, if you treat it as a group of 64 /32 subnets, you can
use all 64 addresses in the /26 that you allocated for web hosting. The
same thing applies to dynamic IP pools on your NAS.
Keep in mind, though, that this does not work if you are not properly
subnetted. If the subnet on your LAN is a /24, you can not use the network
or broadcast addresses. If, however, you use the first /26 (0-31) for your
LAN, then route the last /26 (192-255) to your web server at .10, you can
treat all 64 addresses in 192/26 as /32 subnets, giving you use of all 64
addresses (including .255).
This concept does extend to a /24. If you treat it as a group of 256 /32
subnets, you can use all 256 addresses for web hosting or dialup. It works
for /any/ size CIDR block of IP addresses. Give me a /16, and I'll give you
65,536 usable addresses for web hosting.
--
Troy Settle
Pulaski Networks
540.994.4254
It's always a long day, 86400 doesn't fit into a short
** -----Original Message-----
** From: Colin Campbell [mailto:sgcccdc@citec.qld.gov.au]
** Sent: Tuesday, January 09, 2001 5:38 PM
** To: Troy Settle
** Subject: RE: Hosting with multiple subnets
**
**
** Hi,
**
** On Tue, 9 Jan 2001, Troy Settle wrote:
**
** > Agreed, but you could have given an example of one of the good
** ways to do
** > it. Here's how I set up for hosting:
** >
** > 192.168.10.1/26 - gw address
** > 192.168.10.8/26 - fxp0 on my web server
** > 192.168.20.0/23 - bound to lo1 on the web server
** >
** > I use zebra to implement OSPF to get the routes kicked around
** my network,
** > but it could easily be done with a static route on the gateway router.
** >
** > Doing it like this keeps the arp tables small. I don't know
** if it really
** > matters or not, but I like it like that.
** >
** > I also use a script rather than rc.conf to do my bindings:
** >
** > for i in `jot 256 0`
** > do ifconfig lo1 inet 192.168.20.${i} netmask 0xffffffff alias
** > done
** >
** > And, yes, I do bind the /whole/ subnet. I won't use .0 or
** .255, but with a
** > /26, I will use all 64 addresses.
**
** You cannot use ALL addresses in a subnet. A /26 gives you 62 usable
** addresses. The host address that is all 0's is the sub-network
** address and
** the host address that is all 1's is the broadcast address. With
** a /26 mask
** you have four subnets as follows:
**
** Subnet 1
** --------
** 192.168.10.0 = network address
** 192.168.10.1-192.168.10.62 = usable host addresses
** 192.168.10.63 = broadcast
**
** Subnet 2
** --------
** 192.168.10.64 = network address
** 192.168.10.65-192.168.10.126 = usable host addresses
** 192.168.10.127 = broadcast
**
** Subnet 3
** --------
** 192.168.10.128 = network address
** 192.168.10.129-192.168.10.190 = usable host addresses
** 192.168.10.191 = broadcast
**
** Subnet 4
** --------
** 192.168.10.192 = network address
** 192.168.10.193-192.168.10.254 = usable host addresses
** 192.168.10.255 = broadcast
**
** Colin
**
**
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