[ale] Question on network

Matt Hessel matt.hessel at gmail.com
Thu Jan 23 12:21:38 EST 2014


Also you should know that there are three private ranges you can use:

192.168.0.0/16
10.0.0.0/8
172.16.0.0/19 (172.16.0.0-172.16.31.255)

the one you are in is already class A, you don't need to make the broadcast
domain that big - flat networks do not scale well.

Better to carve out another /24 block in 10.0 and route between them.
On Jan 23, 2014 11:05 AM, "Brian Mathis" <brian.mathis+ale at betteradmin.com>
wrote:

> Here's some information that may help:
>
> The idea of "Class A, B, C" networks is long gone.  In the old days, you
> could generally think of subnets having those classes, corresponding to
> netmasks of 255.0.0.0 (class A), 255.255.0.0 (class B), and 255.255.255.0
> (class C).  This is not strictly correct, but it's good enough for the
> purposes of this discussion.
>
> In modern times we have moved to "Classless Inter-Domain Routing", or CIDR
> subnetting.  This is what you are indicating when you use the "/" notation
> on the end of a subnet, like 192.168.1.0/24.  The / is not simply a
> shortcut to save you typing, but indicates that you are actually using CIDR
> subnets.  The / number indicates how many bits are in the netmask, and some
> of these just happen to match up with the old idea of class-ful networks
> (/8 = class A;  /16 = class B;  /24 = class C), but you can have other
> numbers as well, each one giving you a network with a different number of
> hosts.  You can make a subnet smaller by allocating more mask bits to the
> subnet (/25), or make larger by using fewer mask bits (/23).
>
> Here's a good site where you can play with the IP ranges and subnet masks
> to see how choosing a different CIDR changes your other network parameters:
> http://www.subnet-calculator.com/cidr.php
>
>
> Subnetting is done to isolate broadcast domains -- that is -- if a host
> needs something and it doesn't know who to talk to, it will send out a
> broadcast packet asking anyone to respond.  This happens frequently, and
> many services on your network can do this.  Open up wireshark or tcpdump
> and you can see that there's probably a lot more broadcast traffic than you
> think.  If you get too many hosts on a network, productive network traffic
> can get drowned out by the broadcasts, so you want to try to keep subnets
> to a reasonable size.
>
>
> Regarding gateway/firewall IP addresses.  When a host is talking to
> another host within the local subnet, they talk directly to each other.
> However, if a host is trying to talk to someone outside of the subnet, it
> can't talk directly to it, so it sends the packet to the default gateway
> and says "you deal with it".  The default gateway IP address is just that
> address set aside within the local network for the gateway to use, and has
> no other special properties.  From a subnet perspective, the gateway IP
> address is just another host on the subnet.
>
>
> Given your situation, what you are talking about doing is feasible.  You
> can blow up your subnet to a /16, or even just go to a /23, which will give
> you 510 available addresses.  I don't think there's much harm in going to a
> /16 as long as you don't fill it up, but it's certainly a huge subnet.  You
> don't need to change your gateway IP address (you do need to update the
> subnet mask on that device), but you need to make sure that you don't
> accidentally use that IP for other things (such as if you modify your DHCP
> range).
>
> I think a bigger problem you might have is that since you're out of IPs,
> it means you have 254 hosts already on one subnet, and you're probably
> already seeing performance problems because of that.  You really need to
> consider implementing separate subnets instead of making one big one.
>
>
> ❧ Brian Mathis
>
>
>
> On Wed, Jan 22, 2014 at 10:55 PM, Chuck Payne <terrorpup at gmail.com> wrote:
>
>> Guys,
>>
>> I need to as a question, I am weak on networking. Every where I have
>> worked we had a network guy, so I didn't have to deal with this much
>>
>> Currently were I work I am about to run out of ip's, for now every is
>> 192.168.11.0/24 lets say
>>
>> We are using a Class C ( 10.11.0.0/24 254 Hosts Usable ), our head
>> program was us to move to a class B ( 192.168.0.0/16 65534 Host Usable
>> )
>>
>> My question is this, I currently have a firewall that is my gateway,
>> it is 192.168.11.254/255.255.255.0
>>
>> If I change all the ip's even the gateway netmask from 255.255.255.0
>> to 255.255.0.0 with it work with my gateway? Then can I use any ip on
>> the 192.168.0.0 range with my gateway.
>>
>> So for example I set up the the following to use
>>
>> 192.168.10.0/255.255.0.0
>> 192.168.11.0/255.255.0.0
>> 192.168.12.0/255.255.0.0
>>
>> I am currently reading a few books, but they aren't answering my question.
>>
>> I like to be able for ip to work together with the one fireway. By the
>> way, I know that 192.168.0.0/24 is a private range for a class c, and
>> what I am talking would be better with 10.0.0.0/16, but I am use to
>> working with 192.168.0.0.
>>
>>
>>
>> --
>> Terror PUP a.k.a
>> Chuck "PUP" Payne
>>
>>
>>
>
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